426 



NA TURE 



[September i, 1898 



Prof. Delage was followed by Mr. E. A. Minchin, who 

 commenced with an historical review of the subject. After 

 pointing out that the animal nature of sponges was not definitely 

 established until the middle of the present century, he pro- 

 ceeded to explain that the early theory that sponges were 

 Protozoa was abandoned as soon as histological methods im- 

 proved, and it became known that sponges were composed of 

 tissues, made up of differentiated cells. Three views are, he 

 said, at the present day advocated by different authorities : 

 (i) that sponges are Coelenterates ; (2) that they are Metazoa, 

 but not Coelenterates ; and (3) that sponges are not Metazoa, 

 but constitute a phylum independent of both the Protozoa and 

 Metazoa. The question might be attacked by two methods, 

 the comparative anatomy of adult forms and the tracing of the 

 germ-layers of the larva into the permanent tissues of the adult. 

 He then gave a minute account of the development of Clathrina 

 hlanca, based on his own researches, and indicated with the 

 assistance of wall-diagrams the fate of the flagellated and the 

 granular cells. The conclu.sion he arrived at was that the 

 sponges cannot be considered as Coelenterates ; for, if the larvae 

 of sponges and Coelenterates are assumed to correspond, neither 

 the architecture nor the composition of the adults is in any way 

 comparable ; while if the comparison is based on adult struc- 

 tures, then the larval development of sponges is altogether 

 anomalous and dissimilar to any other known development, 

 since the ectoderm acquires an internal position and becomes 

 surrounded by the endoderm. The evolution of the sponges 

 from the Protozoa must therefore have been quite independent 

 of that of the Coelenterates ; and it is probably in the direction 

 of the Choanoflagellate Protozoa that we must look for the 

 ancestral stock of the sponges, since collar-cells are not known 

 to exist except in these groups. In the discussion which 

 followed, Prof. Hreckel expressed himself as still in favour of 

 the coelenterate theory ; Dr. Vosmaer regretted that he had 

 been asked to speak, because it forced him into a confession of 

 ignorance regarding the point at issue ; and Mr. Saville-Kent 

 urged that the vexed problem of sponge affinities should be 

 fairly approached from the protozoic as well as from the 

 coelenterate basis. The very fact of the possession in common 

 by the sponges and by the fiagelliferous Protozoa of these very 

 peculiarly modified cells, found nowhere else throughout the 

 animal kingdom, suggested forcibly a close phylogenetic 

 relationship between these two groups. Prof. Schulze doubted 

 whether the recent embryological discoveries were sufficient to 

 justify the removal of the sponges from the Coelenterates. 



In the afternoon in Section A, Prof. Haeckel, in a paper 

 entitled " Phylogenetic Classification," developed the principles 

 which he had first enunciated in his "General Morphology," 

 and more recently in his " Systematic Phylogeny" (1896). He 

 regarded the Vertebrates, Tunuates, Echinoderiits, Molluscs, 

 Cnidaria, and Sponges as true phyla {i.e. monophyletic groups, 

 arising from a common stem), but grouped the Annelida with 

 the Arthropoda in the phylum Articulata, and the Cestoda and 

 Trematoda with the Coelenterata. 



Prof, von Graff then demonstrated with the aid of a large 

 map the geographical distribution of the land Planarians ; and 

 Mr. G. C. Bourne gave an account of the "Structure and 

 Formation of the Calcareous Skeleton in the Anthozoa," 

 showing that the corallum of the madrepores is not formed by 

 the calcification of ectoderm cells in situ, but is a secretory 

 product of the cells. 



In Section B, Profs. Heymans and Van der Stricht gave an 

 account of the ultimate ramifications of the nerves of Amphioxus, 

 which they had succeeded in tracing out by adopting the 

 elaborate methods of staining which histologists have ot late 

 years found to yield such excellent results in the investigation 

 of nervous tissues of mammals. 



Prof. Ewart exhibited by means of the lantern some photo- 

 graphs of the zebra-horse hybrids which he has bred in his 

 attem])t to prove or disprove the theory of telegony. He 

 described the striping of the various species of zebra and of his 

 hybrids, and showed that the latter do not closely resemble 

 their sire, a Somali zebra, in the pattern of their coat. The 

 dams of three of these hybrids have since borne foals to horses 

 of their own breed, and one of these foals, now dead, is plainly 

 striped, the second faintly so, while the third shows no striping 

 at all. Prof Ewart is not yet prepared to accept telegony as a 

 scientifically established fact, since the colour-markings of these 

 foals might be explained on the hypothesis of "reversion." 

 A paper on the " Tsetze Disease in Mammals," by Prof 



Kanlhack and Mr. Durham, was read and illustrated by slides, 

 showing the living haematozoan and its relation to the blood 

 corpuscles. The rapid spread of the disease is due to the 

 Tsetze- fly carrying the organisms from infected ungulates to 

 healthy ones as they pass through those deadly regions of 

 Africa known as "fiy-belts." The organisms cannot live in 

 the blood more than three or four days, but reproduction is 

 rapid, taking place in the lymphatic glands and the red 

 marrow ; and thus a plentiful supply is kept up until the host 

 succumbs. Death appears to be due either to the fatal action 

 of some toxin excreted by the organism, or to direct interference 

 with the corpuscle-forming organs of the f)ody. The mere 

 presence of the organisms in the blood is not sufficient to cause 

 death. The authors have not been able to discover any means 

 of securing immunity for domesticated animals ; but, since the 

 wild mammals of South Africa though frequently found to be 

 infected do not die of the disease, they are sanguine of ultimate 

 success in this direction. 



Mr. W. Saville-Kent, who a few years ago showed that the 

 lizard Chlamyaosaurus had a habit of frequently running about 

 upon its hind legs, explained that the habit was not confined to 

 this genus. He had found it to be common to certain species 

 of Iguana, Tupinainbis and Basi/isais. 



In Section C, Prof F. Vejdowsky brought forward some 

 observations on the ova ol Rhynchebnis, substantiating the view 

 expressed by him elsewhere, that the dynamic body known as 

 the " centrosome " originates by the differentiation of the 

 middle part of the "attraction sphere" of the preceding 

 division. Prof Hickson gave a demonstration on themedusteof 

 Millepora, and Prof. Pelseneer communicated two short papers. 

 In Section D, M. Ch. Janet propounded a theory that in the 

 head of insects parts belonging to six primitive segments can 

 be recognised. The anterior three are characterised by the 

 protocerebrum, deutocerebrum and tritocerebrum respectively, 

 and the other three by the appendages — mandible, maxilla and 

 labium. The antennse are regarded by the author as belonging 

 to the second segment. These results are based mainly upon 

 a minute study ot the musculature of the head of the ant. 



M. A. Dollfus discoursed on the geographical distribution of 

 the Isopods of Northern Africa; M. E. Olivier gave a general 

 account of the Lampyridse of the Antilles ; and Prof. E. 

 Bouvier communicated the results of his studies on the external 

 characters of Feripatus. 



On Thursday xaotmvi^, at the Guildhall, an interesting debate 

 on the " Origin of Mammals" was opened by Prof Seeley, of 

 London, and Prof Osborn, of New York. Prof Seeley said 

 that as the Iguanodont reptiles had been regarded as the 

 ancestors of birds, so the Theriodont reptiles had been con- 

 sidered the ancestors of mammals. The discovery of the 

 complete skeleton of Pareiasauriis showed that Theriodesiiius 

 was not a mammal, as had been supposed ; and in the same 

 way, the discovery of the Gomphodont reptiles had necessitated 

 the removal of Tritylodon from the man:mals to the reptiles. 

 Pareiasaurus, Dicynodon and Cynognaihus showed different 

 affinities in different parts of the skeleton, and from the skull 

 of the two former no indication could be inferred of the 

 mammalian resemblances seen in other parts of their skeletons. 

 The Anomodontia appeared to show affinities with the lower 

 living reptiles as well as with more than one type of mammal. 

 The form of the brain if it were available would be evidence of 

 affinity of some value, but the brain-cavity of Anomodonts is 

 imperfectly known, and there is no evidence that the brain 

 filled it. Prof Seeley invited comparison of the quadrate 

 region of the skull in the Dicynodonts and Ornithorhynchus, 

 but remarked on the absence of prepubic bones in the Anomo- 

 donts. He showed that the Theriodont division of the Ano- 

 modonts approached the mammalia in the characters of the 

 teeth and the very small size of the quadrate bone ; while, on 

 the other hand, they suggested affinities with the Labyrinth- 

 odont reptiles in the presence of such cranial bones as the 

 supratemporal, and of intercentra in the vertebrae. Although 

 the parts of the pectoral and pelvic girdles bore a close com- 

 parison with those of the Monotremes, and although in many 

 Theriodonts the skull was typically mammalian in form, the 

 mandibular ramus never consisted of a single piece as in mam- 

 mals. The Anomodonts were not the parents of mammals, 

 but a collateral and closely related group ; and the common 

 parent of both might be sought in rocks older than the Per- 

 mian, perhaps in Silurian or Devonian strata. 



Prof Osborn said that in order to clear the ground for a 



NO 1505, VOL. 58] 



