502 



STANLEY C. BALL 



Tnqfci 



out intercellular spaces. The embryo illustrated by text figure 

 13 had probably been subjected to a considerable degree of 

 contortion. It is noticeable that the blastomeres in well pre- 

 served material are closely in contact with yolk, while in shrunken 

 preparations wide spaces intervene; consequently the blasto- 

 meres are apt to become displaced. In both figures the pair 

 of larger cells is prominent. The mitochondrial mass still 

 remains in one of the macromeres. Text figure 13 shows it 



Text fig. 13 Reconstruction from sections of an embryo of fifteen blasto- 

 meres. mad, 'mac.2, first and second macromeres; mit., mitochondrial mass. 

 X 730. 



Text fig. 14 Reconstruction from sections of an embryo of seventeen blas- 

 tomeres. X 730. 



in the form of a hemisphere held at one pole of the spindle, while 

 in text figure 14 it lies, cresent-shaped, outside the astral fibers. 

 h. Behavior of the mitochondrial mass. Although a careful 

 search was undertaken, no cleavage figure was found in which 

 the mitochondrial mass was first being divided. Between the 

 stages shown in text figure 13 and in figure 20 no intervening 

 step was discovered. However, the condition at a later stage, 

 figure 19, suggests that, as the membrane is drawn inward dur- 

 ing cleavage of the macromere, the mass is too large to remain 

 wholly in one cell and is so constricted that part is handed 



