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The following Reports and Papers were read :

1. Third Report on the Marine Zoology, Botany, and Geology of the Irish Sea.-See Reports, p. 455.

2. Interim Report on the Migration of Birds.-See Reports, p. 473.

3. Fifth Report on the Zoology of the Sandwich Islands.
See Reports, p. 467.

4. Report on the Occupation of a Table at the Zoological Station at Naples. See Reports, p. 474.

5. Report on Investigations made at the Laboratory of the Marine Biological Association at Plymouth.-See Reports, p. 469.

6. Report on the Investigation of the Zoology and Botany of the West India Islands.-See Reports, p. 472.

7. Report on the Compilation of an Index Generum et Specierum
Animalium.-See Reports, p. 473.

8. Report on Physiological Applications of the Phonograph.
See Reports, p. 454.

9. Some Remarks on the Stereornithes, a Group of extinct Birds from South America. By C. W. ANdrews.

A brief history of the discovery of these remarkable birds is given, together with a short account of the more important opinions that have been expressed concerning their affinities.

The structure of the skeleton of Phororhacos, recently described by Ameghino, is considered, and, after comparison with certain other birds, some suggestions are made as to the probable affinities of the genus. Phororhacos is regarded as a true carinate bird, in which, as in the dodo, aphanapteryx, and many others, the wings have undergone reduction through disuse. It seems to have been a highly specialised form, and probably has left no direct descendants: its nearest relatives may perhaps be found among the Gruiformes, especially in the Psophiida and Dicholophi, and it possibly represents a specialised offshoot from the generalised stock which gave rise to these forms. No special affinities with the living Ratitæ are found, and it appears very doubtful whether Gastornis is any way related.

The other genera described by Ameghino are much less completely known; some of them, however, differ so considerably from Phororhacos, and in several cases from one another, that they should probably be referred to several distinct families, as, indeed, has already been done by Moreno and Mercerat. The Stereornithes, therefore, appear to include a somewhat heterogeneous group of birds, whose chief points of resemblance seem to lie in their large size and more or less reduced power of flight. The unfortunate absence of specimens of these interesting fossils from

the European museums renders any detailed comparison with existing forms impossible, so that the opinions expressed in the present paper must be regarded as provisional only.

10. Some Facts and Reflections drawn from a Study of Budding in Compound Ascidians. By Professor W. E. RITTER (University of California).

Numerous recent writers have doubted the genetic unity of the compound ascidians; i.e., they have doubted whether their property of budding, the character which all agree to be the final test of whether an ascidian is simple or compound, has not been acquired more than once. Of these authors I may mention Lacaze-Duthiers, E. van Beneden, Herdman, Seeliger, Lahille, and Sluiter.

In discussing the subject van Beneden has made the apt remark that no zoologist would think of uniting all bud-producing actinians in one group and placing them over against all others that do not reproduce in this manner. In his wellknown report on the compound ascidians of the 'Challenger' Expedition, Professor Herdman not only reached the conclusion that the group is polyphyletic in origin, but he also marshalled his broad knowledge to show that they probably originated at three distinct points from the simple ascidians, and to show also what genera trace their origin back to each of these three starting-points. The author regarded this as one of the most important generalisations reached by his study of the great Challenger' collection.

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Quite recently M. Lahille has proposed an entirely new classification of the Tunicata, in which he ignores budding as a diagnostic character of at most greater than generic importance. That, however, this writer has treated the matter too lightly, whether regarded from a morphological or a physiological point of view, will, I apprehend, be allowed by most students of the group.

It is not my purpose to discuss here a classification of the compound ascidians based on the hypothesis of their polyphyletic origin, but rather to show, first, that they have had such an origin, and, secondly, to consider certain developmental probabilities that are involved in, or, rather, are the necessary results of, such an hypothesis.

In the interest of brevity and clearness my discussion will aim almost entirely at showing that two genera of compound ascidians are, structurally considered, considerably more unlike each other than each is unlike a genus of simple ascidians which, in turn, are widely separated from each other.

The genera to which I refer are Perophora and Goodsiria as representatives of the compound ascidians, and Ascidia and Polycarpa as representing the simple ascidians.

Definitely stated the proposition to be established is this: Perophora and Goodsiria are less closely related to each other than on the one hand Perophora is to Ascidia, and on the other Goodsiria is to Polycarpa.

We will first compare the several genera anatomically, and afterwards the budding in Perophora and Goodsiria; and we may begin with Polycarpa and Goodsiria. Polycarpa is closely related to Cynthia, and still more closely to Styela. The genus is, however, distinctly separated from Cynthia, particularly by its possessing simple tentacles and sexual organs in the form of so-called polycarps.

Goodsiria belongs to the Polystyelidæ, a small family of compound ascidians, founded by Professor Herdman for the reception of several genera that are, as our knowledge now stands, closely related to one another, and well separated from all other compound ascidians, although they certainly have rather close affinities with the Botryllida.

The close similarity in structure between Polycarpa and the Polystyelidæ has been recognised by nearly all investigators who have studied them, and my own work has, I think, shown their kinship to be even closer than has heretofore been supposed. In fact, the resemblance is so close between an undescribed species of

Polycarpa which I have found on our Californian coast and Goodsiria dura from the same locality that I am sure no zoologist would ever think of recognising more than a specific difference between them, did not the one reproduce by budding while the other does not. Two points, however, inust be briefly dwelt upon-one of resemblance, the other of difference.

It is well known that the hypophyseal duct in ascidians is usually situated on the ventral side of the ganglion; but it is also well known that Botryllus forms an exception to this rule, for in this species the duct is dorsal to the ganglion. I find that Goodsiria agrees with Botryllus in this peculiarity. I also find that the only species of Polycarpa which I have examined with reference to the point, viz., Polycarpa pomaria, possesses the same unusual character. In some cases, at least, it is well nigh, if not wholly, impossible to ascertain the relation of the duct to the ganglion without the aid of sections. It appears to me, consequently, that the occurrence of this very exceptional condition in both Polycarpa and Goodsiria, when considered together with their many other close resemblances, adds considerable weight to the belief in their close kinship.

The difference to which I refer is the presence usually of well-marked folds in the branchial sac of Polycarpa and the rudimentary condition or entire absence of these folds in Goodsiria. In the sac of Goodsiria dura there is no trace of folds proper, but two of the five internal longitudinal vessels on each side of the sac are distinctly nearer together than are the others. A similar approximation of these vessels where no true folds exist occurs in numerous species of ascidians, and Herdman has given good reasons for regarding it as evidence of folds that have been lost. The vessels are usually crowded on the folds more than elsewhere; the folds in some cases disappear, but the crowded vessels, being a deeper morphological character, persist though on a plain surface. Now it can be shown that in genera where these folds are present as a rule, but where they may be rudimentary or absent, it is, in a general way, in the larger species that they are best developed, and in the smaller ones that they are rudimentary or absent. From this fact and others I am disposed to look upon Goodsiria as a pigmy Polycarpa.

Next, concerning the structural likenesses between Ascidia and Perophora, they are close in most points and not remote in any. Perhaps the most important difference is found in the branchial sacs, but this difference is interesting. Ascidia has internal longitudinal vessels which are papillated, while Perophora has no internal longitudinal vessels; but it does have long interserial papillæ, each of which is provided with two processes of variable length, one directed anteriorly, the other posteriorly. Now if these processes on one series of the papillæ were to reach across and unite with the corresponding ones of an adjacent series of papillæ, internal papillated longitudinal vessels would be produced entirely similar to those existing in Ascidia. Suggestively enough, individuals of at least two species of Perophora have been observed in which just such a union does exist. From this it would appear that the lateral processes of the papillæ in Perophora are remnants of internal longitudinal vessels; and this fact, taken in connection with others, inclines me to regard Perophora as a pigmy Ascidia, just as we have seen that Goodsiria may be regarded as a pigmy Polycarpa.

In comparing Goodsiria and Perophora on the one hand and Polycarpa and Ascidia on the other, we find a marked contrast in each case in nearly every organ of the body.

Turning to reproduction by gemmation, the buds of Perophora are produced by a proliferous stolon, while those of Goodsiria are formed directly from the body of the parent zooids, the inner layer of the bud being an evagination of the parietal wall of the peribranchial sac. Are these two methods of origin of buds reducible to a common type? I may say at once that a conclusive answer to this query is not yet possible, for the reason that we do not know how the first bud, i.e., the bud from the embryozooid, arises in either genus.

I cannot leave this part of the subject without saying a single word about the epicardium, a structure that is certainly of much importance in connection with the budding of many compound ascidians. The only structures in Goodsiria that

could possibly be called by this name are two broad, shallow pouches at the posterior end of the peribranchial sacs, one for each side. They certainly have nothing whatever to do with the budding, since the buds arise about as far away from them as the size of the ascidiozooids will permit. Furthermore, they do not have the same relations as the epicardium of Clavelina and other ascidians. In Goodsiria and Botryllus, I may add, they are merely parts of the peribranchial sacs; while in other cases they arise in a definite way from the branchial sac.

In my opinion it is an unjustifiable and purposeless forcing of things to attempt to see anything in either Goodsiria or Botryllus that is homologous with the epicardium of Clavelina and other budding ascidians.

Relying chiefly on the evidence from adult structure, we are, then, as it seems to me, obliged to conclude that the compound ascidians have arisen from the simple ones by at least two distinct groups of these latter having independently acquired the property of reproduction by budding. Now, since the processes of evolution are of quite as much scientific interest to us as are its products, we can hardly avoid an attempt to gain some insight into the developmental processes that have been in operation in this instance.

One question we are impelled to ask is whether some cause for the origin of budding in these animals may not be detected here, where it, whatever it is, has been so potent as to produce its effect twice. A possible cause does suggest itself, and I venture to present it to you very briefly. I confess, however, that the venture is made not without some trepidation.

It will be remembered that we have given reasons for regarding Goodsiria and Perophora as simplified or pigmy Polycarpe and Ascidia respectively. It seems to me possible that budding might have arisen in these genera of simple ascidians as a result of the diminution in size and simplification in structure of some of the species; and I am disposed to regard the diminution in size as the most important factor. It appears to me that the smallest species of Polycarpa, for example, have a much poorer chance of survival than do the larger and largest ones, owing to the simple circumstance that they cannot produce anything like so large a number of embryos as do the larger species. The smallest species that I know of this genus is only 3 or 4 millimetres in length, while most of the species reach some centimetres at least in length; and it is a matter of common observation that in the ascidians the size of the ovary and the number of the ova are in direct proportion to the size of the parent individuals. It is certain that the total volume of the sexual products of a large Polycarpa would be many times greater than the entire animal of the small species to which I have just referred; and the ova in the one case are not much, if at all, larger in the one than in the other. The suggestion is that in these cases budding has in some way arisen as a compensation for the diminished power of sexual reproduction.

A developmental question of wider moment than the one just disposed of, and one which I discuss with much greater confidence, is this. If blastogenesis has had two or more wholly independent origins among ascidians, how is the close similarity in the development of the blastozooids of the whole group to be explained? The interest of this question is greatly increased by the fact that not only is the development of the blastozooids much alike in all the species, but also that this development is quite unique as compared with the development of the embryozooid.

In contrasting the development from an embryo and from a bud it is seen that in embryonic development the ectoderm produces the matrix of the test, the peribranchial sacs, and the central nervous system and hypophysial duct, while in the bud we see these four parts of the animal produced by the inner or so-called endodermic vesicle.

Concerning the endodermic, or rather inner vesicle origin of the ganglion and hypophysial duct, I speak with perfect confidence as regards Goodsiria and Perophora, for this confidence rests on my own observations. The case for the Goodsiria bud in particular is as clear as anyone could wish a developmental fact to be.

Enough of the facts are now before us to enable us to state the problem clearly. If the property of budding has been independently acquired by two quite widely separated groups of simple ascidians, how has it come about that the development of the blastozooids agrees so closely, and in such remarkable peculiarities, as the origin of the nervous system, and the peribranchial sac from the outer layer of the embryo and from the inner layer of the bud?

I believe the answer to be that we have before us an excellent case of develop mental opportunism. The inner layer of the bud gives origin to nearly all the organs of the blastozooid because physiological influences working to such a course of development have been stronger than the hereditary influences tending to make the development follow the embryonic method.

The case is particularly interesting because, as I believe, we are able to put our finger on the physiological cause that has been so potent in modifying the direction, not the final result of the mighty force of heredity.

You will remember that the outer layer of the embryo produces the matrix of the test, the nervous system, and the peribranchial sacs. Now observe. The production of the two last-mentioned structures is a purely developmental matter." It concerns the embryonic period only. The organs become separated, or practically so, from their source during this period, and the outer layer has nothing more to do with them, at least functionally. Not so with the production of the test. This is not merely an embryonic matter; it is an enduring physiological matter. The test must be constantly renewed throughout the life of the individual. The outer layer is consequently an active secretory organ from an early embryonal period to the end of the animal's life; and since the outer layer of the bud is merely a portion of the outer layer of the parent or of the stolon, as the case may be, it is at no time an embryonic layer; it is, from the very beginning, a differentiated organ. It has to grow, to be sure; but in addition it has a wellestablished and important physiological function to perform. Very different is it with the inner layer. Its cells are strictly undifferentiated-embryonic, if you will. They do not even have to digest their own food, for they are constantly bathed in the maternal blood. The layer does not come in contact with the external world at any time or at any point. It has nothing to do but to develop. Why should it not relieve the outer layer from producing some of the parts that it produces in the embryo? And it does.

I must hasten to say that this physiological explanation of the peculiarities of ascidian bud development was suggested by Seeliger, though he did not make as much of it as I believe it deserves.

There are several other instances among budding animals where I am inclined to think that assignable functional influences have more or less radically changed the method of development, but time prevents reference to more than one of these. Chun has very recently shown that in Rathkea octopunctata, one of the Medusa, the inner layer of the parent takes no part whatever in the formation of the bud. The buds are produced on the wall of the stomach, and it appears to me highly probable that the ectoderm alone shares in the process, because the endoderm is so completely given over to the digestive function, while the ectoderm cells have much more largely retained their undifferentiated condition owing to their being in great measure protected from the external world by the subumbrella.

11. Outlines of a new Classification of the Tunicata.

By WALTER GARSTANG, M.A., F.Z.S., Fellow of Lincoln College, Oxford.

Professor Herdman's classification of the Tunicata is based very largely upon modifications of external form connected with gemmation and the formation of colonies. It involves, as Professor Herdman himself admits, an unnatural separation of forms admittedly allied, e.g., Pyrosoma and Doliolum, Clavelina and the Distomidae, Diazona and Ciona, as well as to an unnatural approximation of forms whose structure is altogether dissimilar, e.g., Pyrosoma and Calocormus, Perophora and Clavelina.

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