Munson, Organization and Polarity of Protoplasm. 77 c 



vesicle; and its gradual distribution, radialty, to the distant parts 

 of the cytoplasm. As it flows on, it may form large, conspicuous 

 bodies, in the outside cytoplasm, which are entirely distinct from 

 the true aster (fig. 10 and 11), and which never assume the cha- 

 racteristics of an aster, in as much as two asters are never seen 

 in these ovarian eggs. But this metaplasm may so accumulate 

 around the centrosome as to entirely obscure the aster as is shown 

 in fig. 12. 



When it first appears, it is very finely granulär presenting a 

 striking similarity to archoplasm. It is not surprising, therefore, 

 that this substance, which manifestly is metaplasm, has been 

 taken to be archoplasm out of which the aster is finally formed. 

 But, as this substances flows away from the aster and centro- 

 some, it undergoes a change; loses the appearance of archo- 

 plasm; becomes highly granulär, and stains much more deeply. 

 It is in this latter, transformed condition that it assumes the 

 pronounced characteristics of the yolk-nucleus. Fig. 12 makes 

 this clear. 



This substance, which I have shown to be the effect of nucleo- 

 plasm combined with substances in the cytoplasm, evidently 

 serves as food for the living substance of the cell; for there are 

 numerous cases where the aster is not obscured by this substance, 

 nor associated with it; doubtless because it has been ab- 

 sorbed. 



Because of its continuity with the centrosome and aster of 

 the dividing oogonia, and because of its presence in late stages 

 of the growing egg, I take the aster to be a constant feature of 

 cytoplasmic structure. The metaplasm, yolk-nucleus, and archo- 

 plasm are periodic accumulations of synthetic food substances 

 which through the influence of the caryolymph (itself the pro- 

 duct of chromatin) has been especially fitted to be built up into 

 living substance, by the living substance already existing. In 

 other words, growth by intussusception is made possible by this 

 digestion and synthetic preparation of archoplasm, metaplasm, 

 or yolk-nucleus; which, what-ever the name applied to it, seems 

 to be essentially the same substance, having the same history, 

 and the same ultimate uses in the cell. 



I Have shown, elsewhere 1 ), that this centrosome and aster 

 can be traced back to the centrosome and aster of the dividing 

 oogonia; that both in Clemmys and in Limulus, the centrosome 

 and aster persist, as such, during the growth period of the ovum, 

 offen, however, under highly disguised forms, owing primarily to 

 the accumulation of those amorphous elements in these eggs, 

 which serve as stored up foods. 



x ) Munson: Researches on the Oogenesis of the Tortoise, Clemmys mar^ 

 morata. (American Journal of Anatomy, Vol, III, No. 3, 1904.) 



