246 MICHAEL F. GUYER. 



has had to be thrown out of focus but the four chromosomes can 

 be demonstrated there just as clearly. Figs. 186-188 show 

 more clearly the conditions which exist in these four-groups 

 inasmuch as some depth of focus has been added. It is obvious 

 that, as in photos 42-46, where the chromosomes are arranged 

 around the equator of the spindle and the latter is seen from 

 the side, only three of the chromosomes can be photographed 

 as the fourth lies behind the middle one and in a different plane. 

 Such photos as 37 and 41 of polar views reveal the true condi- 

 tion of affairs. Figs. 181-183 show the real constitution of such 

 groups when seen from the side under the microscope where the 

 focus can be shifted. 



Photos 55-64 and Figs. 165-174 show views of five-groups. 

 Photo 61 and Figs. 169-171 represent such a group in anaphase of 

 division. One end is in better focus than the other in the photo- 

 graph; the figure (Fig. 169) reveals the true condition which is 

 as clear cut as if stamped with a die when examined under the 

 microscope. Photos 63 and 64 are of five-groups in which, 

 although the regular chromosomes have divided the X-like one 

 has lagged at the equator of the spindle and is just in process of 

 division. Figs. 167, 168, 172-174 show camera lucida drawings 

 of other somewhat similar stages. 



SPERMATIDS. 



Inasmuch as the secondary spermatocytes were dimorphic the 

 condition is maintained in the spermatids, of which, therefore, 

 there are typically two classes; namely, those which receive four 

 chromosomes (probably eight univalent ones) and those which 

 receive five chromosomes (probably nine univalent). In most 

 cases, at the conclusion of the last division the chromosomes 

 mass more or .less and become a center around which the new 

 nuclear membrane appears. 



Although resting spermatids with reticular nuclei are to be 

 seen, frequently the spermatids seem to proceed to spermio- 

 genesis without a vegetative or resting stage; that is, the chromo- 

 somes seem to mass for the transformation without passing 

 back into the diffuse stage. 



It should be mentioned at this point that some of the spermatid 



