ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 513 



Viviparity and Parasitism.* — V. Faussek refers to his essay of 

 1893f in which he elaborated an interpretation of viviparity as a kind 

 of parasitism within the limit of a species, " a temporary embryonic 

 parasitism of each new generation on its predecessors." It seems im- 

 portant to remember that the embryo may, like an endoparasite, play 

 an active part in securing adaptive arrangements for itself. " The 

 formation of a placenta is the result of the aggressive activity of the 

 embryo." The glochidia of Anodonta, the embryos of some species of 

 Peripatus and dogfish, the state of affairs in Pipa, Salamamlra atra, and 

 so on, are alluded to. Corroboration is found by considering the 

 alternation of generations in mosses and ferns. The author notes that 

 Giard and Houssay have also recognised the idea of embryonic parasitism, 

 but it is surely a fairly common idea. 



b. Histology. 



Twin Nuclei in Various Types of Cells in the Guinea-Pig.J — Maurice 

 Pacaut notes that binucleate cells have been recorded by various histolo- 

 gists, e.g. in the sympathetic ganglia, in the mucous membrane of 

 tongue and palate, and so on. In studying the tissues of the guinea- 

 pig, the author has found many examples of cells with twin nuclei, 

 especially in the cardiac portion of the oesophagus, but also in the tongue 

 and in the skin, and more sporadically in most of the organs. 



Histology of Digestive Tract of Amblystoma Punctatum.§ — 

 G. A. Bates describes the features of the alimentary tract in this 

 Urodele. The mouth cavity is lined by stratified epithelium. Except 

 in these regions where the cells are low, cubical, and non-ciliate, the 

 lining cells are of the ciliated columnar and goblet type. Glands 

 penetrate the tongue from the dorsal surface ; at the base they consist 

 of clear mucous cells ; farther forward the deeper ends consist of true 

 secreting cells with large (zymogen ?) granules in the free ends. 

 Amblystoma differs from Necturus, Proteus and Triton in the presence 

 of cilia in the mouth and of tubular glands in the tongue. The mucosa 

 of the oesophagus is folded longitudinally, has ciliated epithelium, fewer 

 goblet cells, and no muscularis mucosas. Glands are present in the 

 oesophagus of the young, but absent in the adult. The sub-mucosa 

 and muscularis mucosas are present in the stomach. This is lined by 

 the columnar mucous cells peculiar to the Amphibia. The differentiated 

 regions of higher Vertebrates are not present. The intestine is lined 

 with striped columnar and goblet cells ; the duodenum has folds recalling 

 the valvule conniventes of the higher Vertebrates, while at their base 

 are groups of cells suggestive of glands. The epithelium at the begin- 

 ning of the cloaca is composed entirely of goblet cells, these being 

 gradually replaced by a transitional stratified epithelium with columnar- 

 like cells on the free surface. Below the surface epithelium of the 



* Zool. Anzeig., xxvii. (1904) pp. 761-7. 



t Ruaskoje Bogatstwo, 1903. Studien iiber verschiedene Fragen der biologia:hen 

 Evolution. St. Petersburg, 1899 (in Russian). 



\ Comptes Itendus, cxxxviii. (1904) pp. 1241-3. 



$ 2>ft<4 College Series, No. 8 (1904) pp. 411-35 (3 pis.). 



