spermatogenesis 4Q7 



appears in the contraction stage distinct from the dense chromatin 

 mass, and remains so in postsynapsis and the early growth stage 

 (Fig. 217). It is from the first, a small, ovoid, smooth-contoured 

 body, and still shows clearly when the spireme has segmented and 

 the tetrads are forming (Fig. 218), and when the dumb-bells are 

 formed (Fig. 219). It takes an eccentric position in the equatorial 

 plate of the first spermatocyte (Fig. 220). It does not divide in 

 the first spermatocyte division (Fig. 221), and is the last chromo- 

 some to reach the pole in the anaphase (Fig. 222). As there are 7 

 chromosomes, plus the odd one, in the first spermatocyte, so there 

 are 8 in half the second spermatocytes (Fig. 223), and 7 in the 

 others (Fig. 224). The odd chromosome behaves like the others 

 in the second division (Figs. 225 and 226), and is not distinguish- 

 able in the spermatids, all of which have a chromatin nucleolus 

 (Fig. 227). In the development of the spermatid, the chromatin 

 reticulum first becomes massed on the side of the nucleus toward 

 the axial filament (Fig. 228), and then forms a dense U, leaving 

 the rest of the nucleus clear (Fig. 229). The nucleus then elon- 

 gates, still leaving a clear space toward the apex (Fig. 230). The 

 mature spermatozoon has a solid dense chromatic head (Fig. 231 ). 



Aphrophora quadrangularis 



This species was found on the grass and low bushes in July near 

 Cold Spring Harbor. Originally a small quantity of material w^as 

 collected and tried in aceto-carmine, as it was supposed to be the 

 same species that Stevens ('06b) had found in Maine and described. 

 But the reduced number of chromosomes proved to be 11 instead 

 of 12, so material was fixed in Gilson and kept to be studied at a 

 convenient time. The material was obtained from two distinct 

 localities, but not kept separate. The sections showed follicles 

 with II chromosomes and a few with 12. Whether this difference 

 corresponds with the difference in locality it is unfortunately not 

 possible to say. Another peculiarity is that the form with 12 chro- 

 mosomes does not resemble, in some of its stages, the form with 

 12 chromosomes described by Stevens. The most important 

 stages of the form with 1 1 chromosomes are shown in Figs. 232 to 

 242. There are 21 spermatogonial chromosomes (Fig. 232) and 



