SPERMATOGENESIS OF THE DRAGON-FLY. 2J5 



which are not in focus. Figs. 12 and 13 show polar views of 

 telophases of the last spermatogonial division. 



The chromosomes soon fray out into indistinct masses as in 

 Fig. 14. One, however, remains distinct and round in greatly 

 destained preparations and may appear divided in some instances. 

 Figs. 15 and 16 show the round chromosome as a single and as a 

 double body. It is easy to distinguish this stage from the 

 spermatogonium as the chromatin is thickly scattered throughout 

 the cell in indistinct, granular masses. Some of these masses 

 aggregate in the center or toward one side of the nucleus to form 

 a nucleolus and the round body then is indistinguishable, ob- 

 scured probably by the masses which formed the nucleolus 

 (Fig. 17). There is then formed a vague, indefinite reticulum: 

 the inconstant chromatic bodies mentioned as sometimes present 

 in the spermatogonia are never present here. Wilson ('12), in 

 stage A. in Oncopeltus, which is similar, says that in the early 

 telophase, the sex chromosomes cannot be identified while in a 

 little later stage, the sex chromosomes are elongated and the 

 autosomes form a lightly staining, vague net-like structure in 

 which individual chromosomes cannot be distinguished. Davis 

 ('08) and McClung ('02^) also describe a like stage in the Orthop- 

 tera. 



(6) The Changes Occurring in the Growth Period up to and In- 

 cluding Formation of Crosses. 



As to exactly what takes place in synapsis it is hard to assert 

 positively. There is present throughout this period a round, 

 compact, deeply staining chromatin body which can be traced 

 in every stage. This never loses its identity, though it may be 

 obscured in some cells and from its subsequent behavior it can 

 be identified as the sex-chromosome. It seems reasonable to 

 suppose that it may be identical with the dense round body 

 present at the end of the last multiplication period. But the 

 disappearance of this body in the rest stage, although possibly 

 only hidden under chromatin masses, breaks the continuity 

 between the end of the last spermatogonial period and the growth 

 period. 



