No. 2.] ORIGIN OF THE EGG CENTROSOMES. 393 
nucleus. All gradations in size occur, but at a certain stage 
many of the larger ones are approximately equal both in size and 
distinctness. Frequently one can count from fifteen to twenty 
very distinct asters in a single section. These structures cor- 
respond closely to “secondary mechanical centers” of Reinke,} 
and I will call them the secondary asters. While yet distinct 
from one another, they are often so near together that their 
rays intercross. 
It is not long before two of the asters become predominant, 
— primary asters. Their rays increase in number and length, 

Fic. II. — Section of egg free from ovary, Fic. III. — Section of egg in a stage later than 
showing secondary asters. Camera. Fig. II. Only the two primary centers are 
present. Camera. 
apparently at the cost of the secondary asters, for the latter 
gradually evanesce with the further development of the former, 
and at length the cytoplasm possesses only two well-marked 
centers of radiation (Fig. III).2 The primary asters lie near 
the germinal vesicle, usually about go° apart, but their relative 
position is subject to considerable variation in different eggs. 
They are destined to be the asters of the first maturation spindle. 
Each of them has for its center a perfectly definite deeply 
stained centrosome (centriole), surrounded now by a lighter 
area from which the rays diverge. The nuclear membrane 
1 Reinke: Zellstudien II. Arch. f mikr. Anat. Bd. XL, p. 276. Peritoneal 
cells of the larval salamander. 
? The initial predominance and further growth of the primary asters certainly 
appears to be due in part to the actual coalescence of smaller asters. 
