294 N. M. Stevens. 



eating that the fragments disappear somewhat earlier than in 

 Sagitta bipunctata. Figs, 50 and 51 show the remains (k) of the 

 'besondere Korper' in Sagitta inflata; here it is granular and 

 yellowish, not taking the hsematoxylin. My sections all indicate, 

 as Elpatiewsky says, that division of the 'besondere Korper' is 

 unequal, a larger portion going to one of the first two germ cells 

 than to the other. 



As to whether this body is a special device for determining sex 

 in a hermaphrodite organism, I do not think we can safely express 

 an opinion without more evidence drawn from the embryology 

 of other hermaphrodite forms. The special object of my renewed 



H 



Fig. H. Freehand sketches showing relative positions of the two pairs of 

 primary germ cells. 



study of the germ cells of Sagitta at Naples last year was to see 

 whether the division of the first two primary germ cells to form two 

 primary oogonia and two primary spermatogonia is in any way 

 a visibly differential mitosis. I have not been able to detect 

 anything of that nature. Before Elpatiewsky's paper appeared, 

 I had noted the fact that the two primary germ cells never 

 divided synchronously. One finds one cell in prophase, the other 

 in metaphase; one in metaphase, the other in anaphase; one in 

 anaphase, the other in telophase, etc. Having also noticed that 

 the arrangement of the four germ cells in a row is a secondary 

 matter, I had suspected that the differential division might be 

 the earlier one. When the two cells are in mitosis, the two spindles 

 in metaphase often stand nearly at right angles, and one finds 

 the four cells soon after this mitosis in various positions (Fig. H a, 

 h, and c). In the older gastrulse, after the entoblast folds are 

 formed, the four cells usually form a nearly straight row, as in Fig. 

 51. Fig. 52 shows the four germ nuclei in an egg of Sagitta in- 



