NOVEMBEE 1, 1895.] 



SCIENCE. 



573 



tal membranes and appendages of verte- 

 brates. He referred the formation of the 

 amnion to tlie need of protection for the 

 germ when the eggs are laid on land. Me- 

 chanically regarded, the process may be 

 considered as a sinking, first of the front 

 end, and then of the hinder end, of the em- 

 bryo into the yolk sac. The development 

 ment of the allantois as a respiratory organ 

 keeps pace with the sinking of the embrj'o. 

 In the structure and development of their 

 foetal membranes and appendages the mono- 

 tremes stand between the Sauropsida and 

 the higher mammals. 



Prof. Hubrecht (Utrecht) gave a dem- 

 onstration of lemurine placentas. He 

 finds the placentation of Tardus to be en- 

 tirely different from that of Nydieebus and 

 other lemurs. While Nyeticebus has a dif- 

 fuse placenta, in Tarsius the chorion is quite 

 thin and transparent, except at one spot, 

 which forms a discoid placenta, so to speak. 

 This develops at first as a massive cone, 

 which grows into an especially modified 

 part of the uterine wall. The allantois 

 grows into this cone and surrounds the ma- 

 ternal blood vessels. 



Prof. Zograf (Moscow) made a communi- 

 cation upon the teeth of the chondrostean 

 ganoids. The sturgeons possess teeth in 

 the young stages which are preserved longer 

 in the eastern species than in the western. 

 A series may be made from the sterlet (A. 

 ruthenus), which loses its teeth toward the 

 end of the first year, to Psephurus gladius, 

 which retains them tliroughout life. The 

 American Polyodon folium also retains its 

 teeth permanently, but nothiug is known in 

 this respect of the other sturgeons of that 

 continent. It is to be hoped that Ameri; 

 can investigators will soon clear up this 

 point. 



Mme. Celine Renooz (Paris), in a paper 

 on the embryonic development of verte- 

 brates, explained her views as to the deri- 

 vation of aerial animals from plants and the 



vegetable traces which occur in the first 

 stages of embrj^onic development. 



Prof, van Bemmelen (the Hague) pre- 

 sented a paper on the phylogeny of the 

 Testudinate reptiles. The perforated cra- 

 nial roof of the fresh- water turtles, as well 

 as that of the lizards and snakes, must be 

 derived from the uninterrupted roof of the 

 marine forms. In the series of turtles the 

 quadrate has developed into a tympanic 

 ring, probably homologous with that of the 

 mammals. The plastron contains elements 

 of different phylogenetic antiquity ; the an- 

 terior three are the homologues of the epi- 

 sternum and clavicles. 



Prof. Kowalevsky spoke of the lym- 

 phatic glands of Scorpio europams and certain 

 allied forms. In some of these may be dis- 

 tinguished one class of glands which deals 

 with solid substances and the lymphoid 

 glands which prefer dissolved matters. 



Prof Schimkewitsch made a communi- 

 cation upon the first stages of develop- 

 ment in the parasitic copepods. He has 

 observed the segmentation, the formation 

 of the germ layers, the very precocious de- 

 velopment of the germinal cells, and the 

 formation of the nervous system in the same 

 way as in Gammariis as given by Bergh. 



Prof. Gilson (Lou vain) described the 

 special muscular organs which he has dis- 

 covered in the dissepiments of Oivenia. It 

 seems certain that these organs serve to 

 regulate the pressure of the perivisceral 

 fiuid in the different segments and occasion- 

 ally to isolate certain segments. Epithelial 

 tubes situated in the fifth and sixth dissepi- 

 ments and opening externally lead to the 

 septal canal, and seem destined to introduce 

 water into the perivisceral cavity for the 

 needs of the hydraulic mechanism which 

 constitutes the body of this tubicolar an- 

 nelid. 



M. Dautzenberg (Pai-is) gave an account 

 of new molluscs dredged from near the 

 Azores and the coast of Senegal — another 



