48 PETEE OKKELBERG 



cysts, probably to an indefinite number. In Bufo it appears that 

 the cysts do not break up, for, according to King ('08), all the 

 cells of a cyst are descendants of one primary oogonimn in the 

 female, and the cyst wall is formed out of the original follicle 

 cells which surrounded the primary oogonium. Witschi ('14) 

 states that the number of cells formed from the primary oogo- 

 nium in Rana is at least thirty- two in some cases, but often fewer, 

 while in the testis the number is greater. In the turtle Clemmys, 

 Munson ('04) found that the number of divisions was three, 

 each cell thus giving rise to eight cells. 



It is impossible to distinguish oogonia and spermatogonia in 

 the lamprey until the larva is about 35 mm. long. Before that 

 time the cells in all larvae appear structurally alike and divide 

 in a similar manner. The centrosphere with its centrosome 

 corresponds to the yolk nucleus described by Lubosch ('04) 

 in the larvae of lampreys about 4 cm. long. He describes it as 

 an oval, clearly defined body of the same structure as the sur- 

 rounding plasma, but not staining so deeply. Surrounding it, 

 like a membrane, he found deeply staining granules. Lubosch 

 believes that the yolk nucleus introduces the process of yolk- 

 building; but this cannot be its function in very early stages 

 (larvae up to 35 mm. in length) while the cells are still dividing 

 and long before there is any formation of yolk. In these stages 

 it probably functions in ciell division in the germ cells as it does 

 in other cells. During the subsequent growth period it may play 

 some part in the process of yolk-building. 



The vitelline body is probably present in all indifferent germ 

 cells. It seems to be a permanent element in the germ cells of 

 the lamprey, but it was not possible to determine its origin. 

 King ('08) beheves that in Bufo it must be considered as a 

 secretion product of the cytoplasm itself, but she thinks it not 

 improbable that a fluid, possibly an enzyme, may pass from the 

 nucleus into the cytoplasm and there cause the formation of the 

 body, and that this enzyme, while in the nucleus, may be in the 

 form of plasmosomes. Dodds ('10) has described a body in the 

 cytoplasm of the early germ cells of Lophius and believes that 

 it is a mass of plasmosome material that has been separated and 



