SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLiOaY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICBOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. EmtaryologT^.t 



Study of the Vitellus.J— H. Dubuisson has made an elaborate 

 study of the yolk — its formation, degeneration, and utilisation — in a 

 variety of types. In the sparrow the formation of the yolk is preceded 

 by a vacuolisation of the cytoplasm, and the yolk is deposited both 

 centripetally and centrifugally in these vacuoles. In the tortoise there 

 is a formative zone at some distance from the periphery, and the yolk is 

 differentiated on both sides of this. Later on a sub-peripheral forma- 

 tive zone appears. In both sparrow and tortoise there is an apparent 

 retardation of yolk-formation in the immediate vicinity of the nucleus. 

 In amphibians the yolk is formed in concentric zones ; it spreads in two 

 directions ; the nucleus exerts a retardative influence. 



In degenerating ova of the sparrow the process begins with the 

 nucleus ; the follicular epithelial cells proliferate, and act as phagocytes 

 to the yolk, many of them entering it ; the whole cavity of the ovum 

 becomes filled with them ; then there is a migration and a connective - 

 tissue stroma is left. In reptiles some of the follicular cells show very 

 large nuclei ; a number combine and simulate giant-cells ; there is again 

 a penetration of the ovum, and phagocytosis. Similar phenomena are 

 described in other groups, and the general conclusion is reached that the 

 degeneration of ova is due to a phagocytic process on the part of the 

 immediately circumjacent cells. In the same way the author finds thac 

 the process involved in the digestion of the vitellus is phagocytic. With 

 great circumstantiality and with abundance of concrete illustrations the 

 author has made an important addition to Metchnikoff's doctrine of 

 phagocytosis. 



* The Society are not intended to be denoted by the editorial " we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as achially pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. X Arch. Zool. Exp^r., v. (1906) pp. 153-402 (5 pis.). 



2 E 2 



