480 THOMAS n. BRYCK. 



On the dissolution of the nuclear membrane the site of the 

 germiual vesicle is occupied by a " kinoplasmic " mass, 

 derived either entirely from the nuclear network, or also 

 partly from protoplasm differentiated on the distribution of 

 the nuclear substance into it. In fixed material this area has 

 a fibrillar appearance. This may be the result of the fixing- 

 reagents used, but in any case it indicates the accumulation 

 at this part of protoplasm which has undergone some change 

 in constitution physical or chemical. In the nuclear area, 

 out of this material, asters are formed, and ultimately the 

 first polar amphiaster. Besides the asters concerned in 

 the formation of the bipolar figure, there are secondary 

 asters, which seem to have only a temporary existence. 

 In some few cases multipolar figures were observed. No 

 structure recognisable as a centrosome or centiole was found 

 before the germinal vesicle broke down, and therefore the 

 centrosome was either derived from the nucleus, or formed, 

 de novo in the nuclear area. The astral radiations are 

 confined to a small and superficial part of the egg, and a very 

 unequal division results in the formation of the polar bodies. 

 When the two divisions are over all the radiations and the 

 remains of the kinoplasmic area disappear, the cytoplasm 

 assumes its alveolar structure throughout, the nucleus retires 

 from the surface, and no centrosome can be recognised 

 in relation to it. 



On the breaking down of the germinal vesicle the greater 

 part of the nuclear material disappears as such, and not only 

 is a change in the constitution and distribution of the proto- 

 plasm to be recognised, but experiment proves that the egg 

 has undergone a physiological change of state. Whereas a 

 spermatozoon can neither fertilise an egg with the germinal 

 vesicle intact, nor a fragment without the nucleus (Delage, 

 1901), after the polar bodies are formed the egg becomes 

 capable of fertilisation.^ This cytoplasmic maturation, de- 

 pendent, probably (Delage, 1901), on the influence of the 



' For evidence and Uicorics regarding tlic influence of the stage of matura- 

 tion in Anipliibian eggs see Butaillon (1901). 



