CHONDRIOSOMES IN CELLS OF FISH-EMBRYOS 477 



Figures 8a and 8b represent sagittal sections of two myo- 

 tomes from the same embryo. In both, the dorsal edge is formed 

 by cells multiplying actively and moving ventrally to differen- 

 tiate into myoblasts. A frontal section would show the muscle- 

 plate and the cutis-plate; the latter, in fishes, persists much 

 longer than in birds and mannnals. The constitution of the 

 muscle-plate is difficult to elucidate. For birds and mammals, 

 however, I am of those who believe that the myoblasts are well 

 individualized cells; T found ('10, 2) that the distribution of their 

 nuclei does not agree with the syncytial theory and I never 

 failed to see the cell-limits on cross-sections of embryos fixed 

 with Flemming's fluid or a modification of it (Duesberg, '10, 2, 

 figs. 17 and 19). I want to emphasize this viewpoint as opposed 

 to that of Huber ('16), who is inclined to believe that, in the 

 rabbit, "the syncytial character of the cells from which the 

 voluntary muscle is developing is evident" (p. 168). The rea- 

 sons why Huber failed to see the limits of the myoblasts are in 

 my opinion obvious: he used longitudinal sections, when only 

 cross-sections can give the clue, and he made the sections too 

 thin (2 and 3 /x thick), for, the thinner the sections, the less con- 

 spicuous will the cell-limits appear. I desire to call attention 

 also to what I wrote on page 466 about the action of certain fixa- 

 tives on the cell-limits. 



I come now to a consideration of the chondriosomes of the 

 cells of the somites. In the very young myotomes (i.e., before 

 any differentiation of the inner layer has taken place) and later 

 in the cells of the dorsal edge and of the cutis-plate, the chon- 

 driosomes are for the most part long filaments, which may en- 

 tirely circumscribe the nucleus. Figures 8a and 8b show such a 

 disposition very well in the cells of the dorsal edge. 



In the myoblasts, there occur very marked differences in the 

 pictures of these cytoplasmic constituents in the stage before as 

 compared to that after the development of myofibrils. In the 

 first case (fig. 8a), the myoblasts contain very numerous chon- 

 driosomes at both ends and also a large number of these bodies 

 in the intermediate portion of the cell; these intermediate ele- 

 ments are either very long chondrioconts extending to both ends 



