STUDIES ON CHROMOSOMES 367 



Stage b. It is at any rate certain that the telophase-chromosomes 

 in this form retain their identity much longer than in Lygaeus, 

 as is shown by figs. 74 and 75, which are connected by all inter- 

 mediate stages with anaphase-figures in the same cyst. In a 

 recent paper on Euschistus, Montgomery ('11) describes a stage 

 that seems to correspond to my Stage b, and identifies the massive 

 bodies with the telophase-chromosomes. 7 I must confess, how- 

 ever, that neither this account nor my own observations on 

 Euschistus convinces me that this is correct. It seems to me that 

 we have as yet no safe demonstration in any animal that the pre- 

 synaptic chromosomes are actually the same individual chromo- 

 somes as those of the last diploid division. 



I am unable to state in exactly what way the massive bodies of 

 Stage b arise, for there is no way of demonstrating the seriation at 

 this time, and the change is probably effected rapidly. Differ- 

 ent cysts of Stage b vary considerably, the massive bodies being 

 more irregular and less sharply defined in some; but I have not 

 gained any clear idea of the succession. 



Stage c. We may now consider the most interesting changes that 

 take place during the transition to the leptotene stage, the earlier 

 of which may in some cases be seen in the same cysts with the 

 preceding stage. In Oncopeltus and Lygaeus the minuteness and 

 delicacy of the structures are such that I was long in doubt as to 

 how the process takes place; but Largus, Anax, and some of the 

 grasshoppers constitute a series in which the same essential phe- 

 nomenon is seen on a successively larger scale, and which leaves 

 no doubt as to its nature. In all these forms the process involves 

 the resolution of the paler massive bodies into closely convoluted 

 or coiled threads, which then uncoil or unravel to form the leptotene- 

 threads of the succeeding stage. The sex-chromosomes, on the other 

 hand, fail to undergo such a transformation, and retain their mas- 

 sive form, though in some cases (Largus) there is some evidence 

 that they too may have an internal thread-like structure. 



7 Arnold ('08) gives a similar account of a corresponding stage in Hydrophilus, 

 and describes the massive bodies as conjugating directly two by two, before 

 giving rise to spireme-threads. 



