392 Naoliide Yatsn. 



VI. FORMATIOISr OF POLOCYTES. 



In the living egg of Cerehratulus lacteus one observes at the 

 animal pole a depression as soon as the first maturation figure reaches 

 there (Kostanecki, '02, p. 272, cf. Rhumbler's polar depression, '96, 

 p. (i07). In case the egg is fertilized before the dissolution of the 

 geraninal vesicle the polocyte formation follows soon after the matura- 

 tion figure comes to the animal pole. But otherwise the depression 

 remains until the egg is fertilized. Immediately after fertilization 

 a clear drop containing refringent chromosomes and destitute of 

 yolk drops, flows out as though a portion of peripheral hyaloplasm 

 gushed out through a hole. The spinning activity of the polocyte 

 is beautiful as described by Andrews ('98) and C. B. Wilson ('00). 



In sections of the nonnal egg accumulation of hyaloplasm is seen 

 over the animal pole. As the polocyte bulges out, the chromosomes 

 flow in, they being crowded at first in the narrow stalk of the polocyte 

 and finally jiassiug into it. Xo alveoles can be seen in the polocyte. 

 The second one is formed in the same way. A mid-body is formed 

 only between the second polocyte and the egg.^" 



As to the mechanism of the polocyte formation little has been dis- 

 cussed. The processes seem to be of entirely different nature from 

 ordinary cell division. There are two types in the polocyte forma- 

 tion, namcdy, in one class the ])olocyte is formed before and in the 

 other, after fertilizatiou. In the latter, the first maturation mitosis 

 stops at a certain stage and (mlV after the entrance of the sperm 

 is the polocyte formed. It is hardly necessary to enumerate the 

 cases, in which the spermatozoon plays an important role in the 

 reorganization and stimulation of cytoplasmic activity accompanying 

 with it, e. g., contraction, amoeboid movements. An interesting ex- 

 periment performed by Ilertwig nuiy, however, be worth mention- 

 ing here. Tie ])ricked the eggs of Rana tcm.pomria with a glass 

 needle, but uothiug hajjpened until they were fertilized. The extra- 

 ovates are furuied from the wounded eggs only ujion fertilization 



■■'"Tlio nnclous of tlip first polorytc is ;i fonipiict clinmiatiii mass, while tliat of 

 tlK' second is a vesicular one. tlie chi'oniatic l)an(l with Ja.ujied surface coiling 

 .insl lieneatli t]H> nuclear nieniltrane. Division of the first polocyte sometimes 

 1al<('s place. 



