158 GERM-CELL CYCLE IN ANIMALS 



by Patterson (1912) in Graffilla gemellipara, and by 

 Patterson and Wieman (1912) in Planocera inquilina. 

 Patterson and Wieman have given the uterine spindle 

 in Planocera careful study, and have established the 

 fact that in this species it is simply a maturation 

 spindle which forms near the center of the egg and 

 later moves to the periphery, undergoing during 

 this migration a distinct contraction. They further 

 suggest that the uterine spindles described in the 

 eggs of other animals are really one phase in a typical 

 maturation process. 



It has thus been shown that the first maturation 

 spindle in certain eggs may remain practically in- 

 active for a considerable period. It should be noted, 

 however, that in Copidosoma the spindle arises not 

 in the fully grown egg but in very young oocytes, 

 and that it appears to lack asters at every period of 

 its history. While therefore this structure may be a 

 precocious maturation spindle, it differs markedly 

 from any other such spindle that I have been able 

 to find described in cytological literature. 



The second view is that the oocyte spindle repre- 

 sents a special mechanism leading to an accurate 

 distribution of chromatin in the keimbahn-chromatin 

 mass. The position of the contracted and condensed 

 spindle, however, is not definite, since it has been 

 found to occupy almost any part of the oocyte and 

 to lie with its long axis parallel to the long axis of 

 the oocyte, or oblique or even perpendicular to this 

 axis (Fig. 46, E, G). Furthermore the keimbahn- 

 chromatin does not seem to be of a definite structure. 



