Page images
PDF
EPUB

(swimming, diving, running, flying), in feeding, bathing, &c., are instinctive or congenital in their definiteness; and how far the definiteness of these and other activities is a matter of individual acquisition. Observations were also made on congenital and acquired timidity. While the performance of these activities has a congenital basis they are perfected by individual acquisition. There is no instinctive and congenital avoidance of insects with warning colours; that appears to be entirely the result of individual experience. There seems to be little or nothing in the observations to afford any material support to the view that the instinctive activities result from the inheritance of what is individually acquired.

2. Notes on the Early Development of the Ganoids, Lepidosteus, Acipenser, and Amia. By BASHFORD DEAN, Instructor in Biology, Columbia College, New York.

A. Segmentation of the Egg.--The earlier cleavages conform to the usual plan of Teleost and Amphibian :-Lepidosteus and Amia meroblastic, Acipenser superficially holoblastic. Questions as to the kinships with the yolk type of the Elasmobranch on the one hand, and with that of the Teleost on the other, were discussed.

B. Blastula, Gastrula.-The relations of the different forms of Ganoidean blastula were shown in diagrams. The blastula of Lepidosteus and Shark, of Amia and Teleost are similar. Comparison of Ganoidean gastrula: the diagrams show structures diverging from the type of Lepidosteus towards that of Teleost.

C. General Mode of the Formation of the Embryo.-Shark-like characters of Lepidosteus, flattened growth of Acipenser, and Teleostean features of Amia.

D. Conclusions.-Developmental nearnesses of Lepidosteus to the Elasmobranch and of Amia to the Teleost, and the evidence on the side of embryology for connecting the line of the Teleosts with that of the Ganoids, as well as for drawing more closely together the Elasmobranchian and Ganoidean phyla.

3. On some questions relating to the Morphology and Distribution
of Medusa. By Dr. OTTO MAAS.

Dr. Otto Maas exhibited some plates from his monograph of the 'Albatross' Medusa, and discussed some questions arising from the study of these Pacific forms. The collection, though not very rich, is of interest in various points:

1. Morphological. 2. Zoogeographical.

6

3. Bionomical.

1. Amongst 18 species 9 are new, several of them peculiar forms, for instance, a representative of the aberrant genus Homoioneme, established 1892 for some forms of the Plankton' Expedition. Amongst the Acraspeda we find the genera Periphylla, Atolla, and others which are of importance for the morphology of the whole group, and which have induced Claus and Vanhöffen to a reformation of Häckel's system. The previous authors could not study the genital and sense organs; a detailed study of these shows that we can trace a line of relationship from the primitive Lucernarida through forms like Periphylla and Nauphanta to the higher Discophora, forms like Atolla lying a little to the side of the line, whilst Charybdea is totally away from it. The study of the canal system of the Periphyllidæ and their relations shows some primitive features in correspondence with the embryology of the higher forms, i.e., the interruption of the continuous entodermic cavity at four interradial points by the invagination of the Trichterhöhlen.' 2. The Medusa have been caught in an oceanic basin hitherto scarcely explored. In a map of the distribution of the Cathammata given by Vanhöffen the part of the Pacific navigated by the Albatross' is an empty gap which is now filled up.

[ocr errors]

The list of Acraspeda species shows a striking resemblance to that of the 'Challenger' Expedition. The so-called 'deep sea Medusa' seem to have a very

wide geographical distribution; they have been brought home by the 'Challenger,' the Vettor Pisani,' the 'National,' and the Albatross,' but it is to be noticed that they have been caught only in those really oceanic explorations, so, if they are, not deep-sea Medusa, they are certainly not forms of the shallow water.

Amongst the Polypomedusa we find a very close relationship between Atlantic and Pacific species. The different species of one genus are in general much more difficult to distinguish than amongst the Trachomeduse. This perhaps may be explained by the effective power of passive dispersal.

3. For the first time a great number of sketches of living material of the Periphyllidæ, &c., had been obtained on board. All these show the dark purple colour, generally attributed to deep sea animals. The explanation for other forms is, that in the green phosphorescent light of the abysses, purple is the complementary colour, which makes the animal invisible, and acts as a protective colour. It would be dangerous to conclude from this that Periphylla, &c., are deep-sea forms. They have been brought up in an open trawl from a great depth, but the closed part of the net contained no Medusa. If a haul from a great depth contains forms which did not occur in surface hauls, these forms do not necessarily come from the abyss, for they might have been caught on the way to the surface. Our knowledge of the pelagic life of the surface is still so incomplete that every expedition brings us new species, as has been shown in the Copepoda, Medusa, and other groups of the Albatross' Expedition.

4. On the Spermatogenesis in Birds. By J. E. S. MOORE.

The observations were made to ascertain whether the course of the spermatogenesis in birds was essentially similar to that of other vertebrates recently examined. It was found that in two points of chief importance, namely, the manner of numerical reduction of the chromosomes and the alternation of the homo- and heterotype divisions, the spermatogenesis of birds is closely similar to that of the remaining vertebrate forms.

During the first heterotype division, which corresponds to the division of the growing cells in Mammals and of the great spermatocytes in Elasmobranchs and Amphibia, the spermatic elements of pigeons show a marked tendency towards the formation of multinucleate masses. One of the most interesting features appertaining to these bodies is that the spindle-figure during the division of their nuclei appears to originate entirely within the nucleus, since the nuclear wall can be distinctly seen after the spindle-figure has been fully formed. The stages in the division may be diagrammatically represented thus:

C.

wn

Multinucleate Spermatocyte of Pigeon.

(a) Nucleus in synaptic phase. (b and c) Spindle-figures. (un) Nuclear wall. The advent of the great heterotype mitosis is always preceded during the spermatogenesis by the peculiar convoluted and lop-sided figure (a) which is

here, as elsewhere, characteristic of what I have previously termed the 'synaptic phase.'

The whole course of the spermatogenesis appears to correspond more closely with that of Elasmobranchs than of Mammals, since there appear to be two generations and one division after the synapsis before the spermatozoa are complete.

As in Elasmobranchs and Mammals, the number of the chromosomes appears to be reduced during the synapsis, and to be then determined for succeeding divisions, just as in the case of plants.

The spermatogenesis of birds supports in every way the conclusion first put forward by Strassburger, which is at present gaining ground, namely, that the process of numerical reduction in the chromosomes is not brought about by any division at all, and is similar for both animals and plants.

5. On the Development of the Teeth in Certain Insectivora.
By M. F. WOODWARD, Demonstrator of Zoology, R.C.Sci. Lond.

In the hedgehog the author describes vestigial calcified milk predecessors to the third upper incisor, the lower canine, and the first pre-molar of both upper and lower jaws, and an uncalcified vestige of the milk predecessor of the second lower incisor, thus extending Leche's observations and confirming his later conclusion that the adult incisors, canines, and pre-molars all belong to the third or replacing tooth series. In addition, a vestigial anterior lower incisor and a third lower pre-molar were observed. Indications of three dentitions are described for the molar series, the molars being referred to the third or replacing dentition.

The teeth of Gymnura, Sorex, Talpa, Centetes, and Ericulus are also dealt with, and the following points more especially noted:

1. The presence in Gymnura of five pre-molars in both upper and lower jaws, represented in both dentitions.

2. The absence of the alleged milk predecessor to the first pre-molar of Talpa described by Spence Bate, that tooth being shown to be itself a milk tooth.

3. The development, in all cases, of the successor to the fourth pre-molar between the 'deciduous pre-molars 3 and 4.' The facts associated with this appear to indicate that the so-called 'deciduous pre-molar 4' is a precociously developed molar, and that the tooth which replaces it is a much retarded premolar of the milk series.

Two sets of calcified teeth are shown to be for the greater part developed among Insectivores, and it is characteristic of them that there is a tendency towards reduction of the milk set with early development of the replacing dentition.

6. On the Mammalian Hyoid.1 By Professor G. B. HOWES.

The author proved from the study of Nasua that the small bone attached to the paroccipital process in Lepus and Procavia (Hyrax), independently described by Krause and Brandt, is in reality the styloid, and showed that the discovery enables us to recognise two distinct culminating types of modification of the hyoid of mammals, viz. (i.), the protero-stylic, known only in man and the marmosets, and (ii) the opistho-stylic, known only in the rodents mentioned. Reviewing the subject more generally, he called attention to the presence of a considerable tympano-hyal, occupying a novel position, in Cholapus, and he exhibited the hyoid of a young rabbit, the body of which was subdivided by a transverse suture, probably indicative of the original demarcation-line between its two component copula. A classification of the types of mammalian hyoid was submitted.

1 Paper will be published in Jour. Anat. and Phys., Jan., 1896.

7. On the Poison Apparatus of Certain Snakes.
By G. S. WEST, A.R.C.Sci. Lond.

The author describes, in thirteen genera of Opisthoglypha, a gland, which, there is every reason to believe, is homologous with the poison gland of the Viperine and Proteroglyphous types. The course of the poison duct and its detailed relationships to the teeth are dealt with, the latter being established through the mediation of a cavity enclosed within muscular folds, and so effected that loss of the tooth does not in any way result in injury to the duct. The distal portion of the duct is shown to be secretory and mucus-forming.

In the marine snakes (Hydrophiina) the poison gland is shown to be more or less free from the supra-labial, and to consist of longitudinally disposed tubules converging anteriorly towards a central duct. The latter is shown to become enlarged anteriorly, enclosing a cavity in front of the bases of the grooved teeth having muscular walls and specialised for purpose of communication with the grooves.

Certain vascular folds of the buccal mucous membrane are described, which occupy the interstices between the teeth, and are probably analogous to the villous processes occurring in the mouths of certain soft-shelled Chelonians.

8. On the Value of Myology as an Aid in the Classification of Animals. By F. G. PARSONS, F.R.C.S., Lecturer on Comparative Anatomy at St. Thomas's Hospital.

The paper contains a short notice of the reasons which induce Systematists to place little reliance on the study of muscles. It then reviews some of the muscles in the great order of Rodents, and points out how closely they correspond in animals which are nearly related, and how little the different modes of life of their possessors affect them. The ease with which different sub-orders and families of Rodents can be distinguished by a study of their muscles is next noticed, and finally the test of myology is applied to the family of Dipodidae, the position of which is still unsettled.

9. On Ultimate Vital Units. By Miss NINA LAYARD.

1895.

3 B

SECTION E.-GEOGRAPHY.

PRESIDENT OF THE SECTION-H. J. MACKINDER, M.A., F.R.G.S.

THURSDAY, SEPTEMBER 12.

The PRESIDENT delivered the following Address :

[ocr errors]

THIS is a memorable year for English students of geography. We have entertained in London for the first time a great gathering of our foreign colleagues, and have presented to the British public the unfamiliar spectacle of a geographical meeting, in which scholars and professors were as prominent as explorers. As a nation we may justly claim that for several generations we have been foremost in the work of the pioneer; nor need we view with dissatisfaction our contributions to precise survey, to hydrography, to climatology, and to biogeography. It is rather on the synthetic and philosophical, and therefore on the educational, side of our subject that we fall so markedly below the foreign and especially the German standard, and it is for this reason that we may regard the Sixth International Congress as a noteworthy object lesson for English geographers and teachers. The time seems, moreover, to have been ripe for some such stimulating influence. To indicate a few signs only of rising courage among our geographers, and of sympathy on the part of the public, I would draw your attention to the institution of afternoon meetings in Savile Row for the discussion of technical questions, to the success of the new Geographical Journal, notwithstanding its geographical as opposed to merely adventuring' flavour, to the recent formation of a geographical association of Public Schoolmasters, and to the demand for addresses on the teaching of geography on the part of the local branches of the Teachers' Guild. Facts are reminding us once more that the lapse of a certain time is essential to the rooting of a new idea, and we may thank the geographical veterans of 1869 for sowing seed the fruit of which we are now harvesting. That I am not alone in my interpretation of present tendencies is clear from the emphatic opinion of the President of the Royal Geographical Society expressed in his last annual address, that the time is approaching for a reconsideration of the educational policy of the Society.' It would almost seem that we are nearing a development of geographical education not unlike that which nine years ago followed on the publication of Mr. Keltie's valuable Report. At that time two of my predecessors in this chair, Sir Frederick Goldsmid and Sir Charles Warren, thought it not unfit to make education the chief theme of their addresses, and encouraged by their example I venture, under present circumstances, to call your attention once more to that subject. Since 1886 and 1887, however, much has happened, and we no longer need to discuss the more elementary teaching of geography. I propose, therefore, to treat of comparative and philosophical geography in relation especially to secondary and university education, and it seems to me that an historical rather than an a priori discussion gives best promise of result.

« PreviousContinue »