16 SUMMARY OF CURRENT RESEARCHES RELATING TO 



associated respectively with the vascular and non-vascular parts of the 

 omphalopleure. It would seem that the former possibly serves mainly 

 for gaseous interchange, while the latter is concerned with the absorption 

 of nutriment. In the non-vascular region the omphalopleure is attached 

 to the uterine epithelium by large pseudopodia-like processes arising 

 from the cells, and ultimately producing degeneration of the uterine 

 epithelium, so that maternal and foetal tissues become very closely 

 connected. As in Perameles, the yolk-sac placenta is contra-deciduate 

 in type. Further, as in Perameles, delivery takes place through a 

 median passage, formed at birth by a rupture of the connective-tissue 

 between the median vagina and the urinogenital sinus. This was de- 

 monstrated clearly in animals killed during parturition, and it was also 

 found that the passage rapidly closes up after birth, and must he formed 

 anew at each parturition. 



Chondrocranium of Chick.* — W. Tonkoff states that the development 

 of the skull in the common fowl has hardly been studied at all since the 

 publication of Parker's work in 1869. In devoting himself to the task, 

 he has begun with the study of the chondrocranium, and finds that it 

 attains its fullest development in the chick at the age of ten days 

 eighteen hours, while at the same time the foundations of the membrane 

 bones have been laid. He sectioned the skull at this stage, and recon- 

 structed a model from the sections. The present instalment of his work 

 is taken up with a description of the model, and a comparison with 

 Gaupp's model of the chondrocranium of Lacerta. Among the points 

 of special interest may be noticed the fact that that part of the squamosal 

 which unites with the quadrate arises from a cartilage which is histo- 

 logically indistinguishable from the cartilage of the chondrocranium, 

 and that the vomer has a paired origin. 



Air-sacs of the Chick. t — Prof. D. Bertelli gives an account of the 

 development of the air-sacs, which he proposes to call cervical, inter- 

 clavicular, anterior intermediate, posterior intermediate, and posterior, 

 and discusses the morphological nature of the bird's oblique septum as 

 distinguished from a true diaphragm. 



Development of Excretory Organs in Turtles. J — Miss Emily Eay 

 Gregory has studied embryos of Aromochelys and Platypcltis, chiefly 

 the latter, with reference to the development and relations of pronephros, 

 mesonephros, and metauephros. She finds that the pronephros arises 

 from outgrowths of the posterior regions of somites 4-10, and that it 

 displays such variations in development as might be expected in a 

 rudimentary organ. The posterior tubules are more or less fused with 

 mesonephric elements, and function as excretory organs. The meso- 

 nephros may extend anteriorly over much of the pronephric region, and 

 its tubules fuse with those of the latter organ. The metanephros arises 

 at the point where the ureter branches from the upper side of the Wolffian 

 duct, and in the blastema surrounding the ureter. It is independent of 

 the mesonephros, save for the connection at the Wolffian duct, and per- 

 haps the participation of a few cells from the mesonephric blastema. 



* Anat. Auzeig., xviii. (1900) pp. 296-304 (1 fig.). 



t Atti Soc. ToBCana, xvii. (1900) pp. 145-66 (1 pi.). 



% Zool. Juhib. (Abt. Anat.), xiii. (1900) pp. 683-714 (6 pis.). 



