KOFOID. — LAWS OF CLEAVAGE. 193 



(2.) The spindle of the cell b 2 in Figures 8, 9, indicates that the 

 products of its division will lie upon the upper left side of the cell 

 b, the upper derivative being in contact with the cell b 3 and with the 

 lower derivative. Blochmann's interpretation, on the other hand, 

 throws the upper derivative completely out of the quadrant of 

 the cell b, and over upon the cell c of an adjoining quadrant. The 

 position of the cells a z -d z and a 2 l -d 2 l , as figured by Blochmann in 

 Figure 10 can be explained only on the assumption of a rotation 

 of both sets of spindles (or of the upper derivatives of the spin- 

 dles) as shown in Figure 9 about ninety degrees to the left. The 

 fact that he has not observed such a rotation renders its existence 

 all the more improbable. 



There remains, however, important evidence in favor of Bloch- 

 mann's view, namely the presence in the cells a 2 and c 2 of " eine 

 Anhiiufung von kleinen stark lichtbrechenden Kornchen." After 

 the cell divisions indicated in Figures 46, 47 (Plate II. Figs. 8, 9), 

 all of these granules are found in the cells a 2 and c 2 , hence the 

 idea of their derivation from the cells a 2 and c 2 . Such a view must 

 presuppose (1) that in the equal division of the cells a 2 and c 2 all 

 of these granules go to on$ of the supposed daughter cells, i. e. 

 to a 2 and c 2 ; (2) that granules similar to those of the cells a 2 

 and c 2 cannot arise in other cells derived, like a 2 and c 2 , from 

 the macromeres. If, on the other hand, the view advanced here 

 as to the interpretation of Figure 48 (Plate II. Fig. 10) is correct, 

 we may suppose that in the equal division of the cells a 2 and c 2 the 

 granules accumulated in them were shared by the two daughter 

 cells o„ and a 5 , c 2 and c 3 (using Blochmann's designations, but not 

 his interpretation), and thus the granules were divided and be- 

 came less conspicuous. At the same time the cells a 2 l and c 2 of 

 the third set of micromeres, originating, as I believe they do, 

 from the macromeres b and d, show granules similar to those of 

 the cells a 2 and c 2 of the second set of micromeres. This may 

 afford an escape from the dilemma as to the relation of these 

 groups of cells in which Blochmann is placed by the contradic- 

 tory evidence afforded on the one hand by the position of the 

 spindles, on the other by the presence of the granules in the 

 cells. 



With regard to the origin of the cells of the quartet a 2 n -d 2 n 



of Figure 50 (Plate II. Fig. 11), I wish to present a view which 



differs from that of the author. As the nomenclature indicates, 



he derives this group from his quartet a 2 l -d 2 of Figure 48 (Plate 



vol. xxix. (n. s. xxi.) 13 



