72 THE AMERICAN ARBAGIA 



TABLE I 



SIZE OF OOCYTE, GERMINAL VESICLE AND NUCLEOLUS DURING GROWTH 



D([x) 



Very young 14.3 



Pigment present 33 



Jelly present 60 



Largest 74 



V((x3) D((.) 



12.8 

 22 



113,100 30 

 212,200 38.4 



i»53i 

 18,820 



V((Z3) 

 1,098 



5>575 

 1 4, 1 40 

 29,650 



4.8 

 9-6 



ID 

 II. 2 



57-9 

 463.2 



523-6 

 735-6 



V ((x3) 



433 



i3>245 



98,960 



182,550 



b. Structure of the Oocyte. Plate II 



The immature egg when fully developed consists of cytoplasm and 

 germinal vesicle, usually excentric. The cytoplasm consists, like that of 

 the mature egg, of a matrix or ground substance in which are scattered 

 spherical oil droplets, yolk granules, spherical red pigment granules 

 or vacuoles, mitochondria, and microsomes. All the granules are scat- 

 tered through the cytoplasm except the mitochondria which form a 

 thick layer around the outside wall of the germinal vesicle; this can 

 easily be seen in eggs stained with methyl green. The fully formed 

 germinal vesicle is about 38 y. in diameter, and contains a vesicular 

 nucleolus, usually excentric, about 1 1 (j. in diameter, often with one 

 or many small bodies or nucleolini within it (see also R. D. Allen, 

 1951b). 



When fixed in Bouin's solution and stained with Heidenhain's 

 haemotoxylin, the nucleolus is quite black, and there is a black staining 

 network through the germinal vesicle (E. B. Harvey and Lavin, 1944) ; 

 (Photographs 17 and 18). Excellent photographs of sections of the 

 immature Lytechinus ( Toxopneustes ) tgg thus prepared are to be found 

 in Wilson's (1895) Atlas of Fertilization, Plate I. The appearance of the 

 immature egg with ultraviolet light is similar to that in the stained 

 preparations (E. B. Harvey and Lavin, 1944). The nucleolus and 

 chromatin network are absorbing and appear black in photographs 



