48 T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



micromeres, those [)roduced b}' E arc somewhat smaller in size than the 

 same budded off from M. The succeeding divisions result in the forma- 

 tion of micromeres alone, the number of macromeres remaining eight 

 for a comparatively long period. The accompanying table gives the 

 order of the cleavage up to the 64-cell stage. 



Of the micromeres in the i6-cell stage, e. i , \. e., the cells produced 

 by E, divided each into two daughter cells of somewhat different size, 

 of which that situated nearer the median plane {c. i. i) is somewhat 

 larger than the other i)iaced awa\- from it {e. i. 2). At about the same 

 time, but a little later, a second micromere (c. 2) is budded off from E 

 (fig. 11); this micromere is nearly as large as e. i. 2. We have now 

 the 24-cell stage before us. This stage soon turns into the 28-cell 

 stage, through an equal division of in. r by a vertical furrow (fig. 12). 

 Directly succeeding this, m. 2 is given off close to in. i. 2 (32-celi 

 stage). Then a fairh' long pause of cleavage sets in, and after that 

 e. I. I and c. i . 2 are divided, the former unequally and the latter equally 

 {e. I. I. I > c. I. I. 2.\ c. 1.2. I = e. I. 2. 2) (40-cell stage) (fig. 13). 

 Soon later, c. 2 undergoes equal division by a vertical furrow (44-cell 

 stage), and then comes an interval of cleavage again. After the interval, 

 m. I. I and in. i. 2 cleave unequally {m. i. i. i > m. i. i. 2\ in. i. 2. i 

 '> m. I. 2. 2), and nearly simultaneously, e. ? is given off. This is a 

 large cell which measures about one half of E in diameter (56-cell 

 stage). Next, in. 2 divides equally b\' a vertical furrow (60-cell stage) 

 (%• H)- Then, the divisions of the macromeres set in.. In these 

 divisions, the cleavage furrow advances in the direction the reverse of 

 that of the first three divisions already described, the cleavage beginning 

 at the animal pole and ending at the vegetative. Of the macromeres, 

 M divides prior to E, giving the 64-cell stage. 



^ta^e i() 24 2S 32 40 44 56 60 64 



M \ V <M I 



<m-2.i- 

 m.i.i- 



/ni.l.l ^m.i.i 



_/ ^111. 1. 1 



\.n.i.2 <^'"-^ 



in. 1. 2.1- 



2.2 



\ 

 e.2- 



e.3- 



< 



0.2.2- 

 e.2.i- 



0.1/ ^^'i 



\c.I.2 ■- <^'^ 



^^e.1.2. 



e.i.i.i- 

 2- 



e.i.2.i 



