Oct. 1 6, 1884] 



NA TURE 



601 



Clepsydrops shows that it has the mammalian number of bones 

 in its tarsus, and the resemblance was nearest to that found in 

 Platypus anatinus. 



Dr. C. H. Merriatn read a paper on the hood of the hooded 

 seal (Cystophora cristala), describing it as an inflatable pro- 

 boscis overhanging the mouth, and extending posteriorly to a 

 point behind the two eyes, lined with nasal mucous membrane, 

 and divided longitudinally by two cartilages. It is not noticeable 

 until the male has reached its fourth year. 



In a paper on some points in the development of pelagic 

 teleostean eggs, Mr. G. Brook, Jun. , first considered non-pelagic 

 eggs, instancing those of trout, in which the hypoblast originates 

 as an involution of the lower layer upon itself, the space between 

 the layers being quite distinct. In pelagic eggs the process is 

 quite different. Sections of the eggs of Trachinus vipara at 

 this stage show that the parablast of Klein, the intermediate 

 layer of American authors, is made up of a large number of 

 free cells, and nuclei are absorbed from the yolk, which con- 

 tribute to a very great extent to build up the hypoblast. In this 

 case there is no true invagination. In Motilla mustela the origin 

 of the hypoblast is similar to that of Trachinus ; but the result- 

 ing cells, instead of being quite similar to the original ones, as 

 usual in teleostean eggs, are very much larger, and hexagonal, 

 so that they cannot be derived directly from the lower layer of 

 cells. The author sustained the views of Ryder as regards the 

 segmentation cavity in pelagic eggs. He also holds that there 

 is no circulation in pelagic embryos before hatching. 



Mr. G. Macloskie, in a paper on the dynamics of the insect's 

 test, commenced with a general description of the chitinous 

 skeleton with its in- and out-growths, &c. The tracheae have 

 spinal crenulations, which have been hitherto misunderstood 

 and supposed to be threads ; these tracheae transmit gases 

 directly to the tissues, and the blood is not used for this purpose. 

 The trachea? are not directly controlled by muscles, their action 

 depending on the successive production of a partial vacuum, 

 and condensation of air around them. 



Prof. A. Hyatt read a paper on the larval theory of the origin 

 of tissue, stating that the building-up of the tissues of the 

 Metazoa is due to a quick and rapid division of cells. Minot's 

 theory that the origin of the sexes is due to the difference in 

 cell elements was supported. The author considered the Planula 

 a more primitive form than the Gastrula. In another paper 

 Prof. Hyatt presented objections to some commonly-accepted 

 views of heredity, asserting that heredity has no need of the 

 gemmule hypothesis or pangenesis, but that it can be equally 

 well understood upon the supposition that the nuclei of cells are 

 the immediate agents of the transmission of characteristics. The 

 author presented the case of a man in Maine, who resembled his 

 mother on one side of his body and his father on the other side, 

 as an illustration of his theory, and he contested the position of 

 Prof. Brooks as regards heredity. In a paper on the structure 

 and affinities of Beatricea, the same author stated that this fossil 

 has had many positions assigned to it in almost all the groups 

 of the Invertebrata, though he himself now thought it a Fora- 

 minifer. Thin sections were examined, the structure being 

 found to consist of cells joined by a stolon. 



Dr. C. S. Minot presented a paper on the skin of insects. 

 The skin consists of three layers — externally the cuticula, over- 

 lying an epithelium, which lies in turn on a sheet of connective 

 tissue ; the epithelium is homologous with the epithelium of 

 other animals, and should be so called instead of hypoder- 

 mis ; and dermis, which should be applied to the connective 

 tissue, as it is the homologue of that of vertebrates. The cuticle 

 of caterpillars has not yet been fully described : it consists of 

 two layers, a thick one and a thin one. 



In a communication on the development of Limulus, Mr. J. 

 S. Kingsley stated that the account begins after the formation of 

 the blastoderm. At this time there is a single layer of cells sur- 

 rounding the yolk, in which are scattered nuclei. The meso- 

 blast arises as a single sheet on the ventral surface. Its cells 

 come largely from the blastoderm, but some arise from the yolk 

 nuclei. The mesoblast soon forms two longitudinal layers, one 

 on each side in the neighbourhood of the limbs. The ccelom is 

 formed by a splitting of the mesoblast, and at first consists of 

 a series of metameric cavities extending into the limbs. The 

 supra-cesophageal ganglion arises by an invagination of the epi- 

 blast. The heart arises as two tubes in the somatophore, which 

 later unite. The mesenteron does not appear until after hatch- 

 ing. The amnion of Packard is the first larval cuticle, and 

 bears no resemblance to the amnion of the tracheata. A second 



cuticle is formed and moulted before hatching. The eyes appear 

 on the dorsal surface at the same time that the limbs appear on 

 the ventral. In these characters Limulus agrees essentially 

 with the Tracheata, and has nothing in common with Crustacea. 



Prof. B. G. Wilder, in a paper entitled, " Do the cerebellum 

 and oblongata represent two encephalic segments, or only one?" 

 remarked that most writers had considered two segments to 

 exist. The cephalad of these segments is held to include the 

 cerebellum, together with the portion of the "brain-stem" 

 immediately connected herewith and the latter part of the 

 oblongata. The only writers that have admitted of a single seg- 

 ment caudal of the mesen are Balfour, A. M. Marshall, Owen, 

 and Spitzka. The views of Spitzka were then discussed, con- 

 cluding with the opinion that sufficient evidence to settle either 

 side was insufficient, and that the question was still open. 



Dr. J. A. Ryder presented a paper on the morphology and 

 evolution of the tail of osseous fishes. The caudal fin of fishes 

 is developed in the same way as the median or unpaired fins, 

 from a median fin-fold. After the protocercal stage of the larva 

 is passed, a lower caudal lobe grows out, which is probably the 

 homologue of a second anal fin. The hypotheses which grow 

 out of a consideration of the facts of the development of the tails 

 of fishes are the following : — (1) Whenever heterocercality 

 manifests itself, there is a more or less extensive degeneration of 

 the caudal end of the chordal axis, which began to be somewhat 

 manifest far back in the phylum in such forms as Holocephali, 

 Dipnoi, and Chondropterygians. (2) With the outgrowth of the 

 lower lobes (second anal) the energy of growth tended to push 

 the tip of the chorda upward ; the lobe itself arising, probably 

 in consequence of the localisation of the energy of growth and 

 the deposit of organic material at the point, according to the 

 demands of use and effort. (3) Local use and effort, acting as 

 constant stimuli of local growth, carried the heterocercal condi- 

 tion and its accompanying modification of degeneration and 

 reduction still further, as is shown by a study of the homologous 

 elements in the tails of fishes ; while use and effort would also 

 continue to augment heterocercality, until the inferior and 

 superior lobes were of about the same length and area, when the 

 morphological characters of the caudal fin would become 

 approximately stable for any one species, as may be shown by 

 measurements of a simple mechanical illustration, in which the 

 interaction and composition of the faces which are brought into 

 action are demonstrated. (4) The mechanical demonstration 

 alluded to above, taken together with the fact that the primitive 

 or ancestral form of the tail, which is typified by a temporary 

 condition in fish larva;, when the myocomata are rudimentary, 

 but still symmetrical, amounts almost to a demonstration of the 

 principles first laid down by Lamarck, then elaborated by 

 Spencer, and more recently applied to special cases by the 

 author and Prof. Cope. 



In a communication on growth and death, Dr. C. S. Minot 

 gave the results of 10,000 measurements of weight of growing 

 guinea-pigs and other animals from birth to maturity. The rate 

 of growth was found to steadily diminish from birth onward ; so 

 that the loss of power begins at once, and continues until death. 

 The common views of death were discussed, and the current 

 conceptions of animal individuality were attacked. The author 

 then referred to the bearing of our present knowledge of 

 senescence upon the theory of life, and the relation of life 

 to a material substratum. 



A paper on the osteology of Oveodon was read by Mr. W. B. 

 Scott, in which this genus was said to belong to the Artiodactyla,, 

 although there are some strong resemblances to the Suidse. The 

 vertebrae are ruminant, markedly in the case of the axis. The 

 thoracic vertebrae have long prominent spines, and small bodies 

 slightly amphiccelus. The lumbars, probably five in number, are 

 heavy, with short spines and broad flat transverse processes. The 

 sacrum contains two vertebrae which touch the ileum. The tail is 

 long and slender, and the legs proportionally long. There are a 

 short head and short metapodials, giving the animal a wolf-like 

 appearance. The radius and ulna are distinct. The carpus 

 consists of eight bones, including the pisciform. There are short 

 unanchylosed metacarpals. The ungual phalanges are long and 

 pointed, as in Hyopotamus. A rudimentary pollex is present, 

 this being the only Artiodactyl with one. 



Mr. J. Struthers, in a paper on finger muscles in Megaptera 

 longimana, and in other whales, records rudimentary flexor and 

 extensor muscles in these animals, and shows that they are more 

 or less used, as the muscular fibres are red and not degenerated. 



Dr. G. M. Sternberg described his experimental research 



