STUDIES ON CHROMOSOMES 369 



These stages have been described in Oncopeltus mainly be- 

 cause of the importance of following the sex-chromosomes at 

 this period; but, as already mentioned, they are shown more 

 clearly in Largus, spermatogonial telophases of which are shown 

 in figs. 74 and 75, and Stage c in figs. 76 to 78. Photos. 26 and 

 27 show nuclei of this form in Stages b and early c, the character 

 of which I hope will appear in the reproductions. The threads 

 are here coarser and show a more definitely spiral disposition, 

 especially evident as the uncoiling progresses. This is clearly 

 evident in many nuclei in the negative from which photo. 27 is 

 reproduced. Though these nuclei are still rather small, they 

 afford demonstrative evidence in regard to the main fact. I 

 am further confident that the threads are separate and undivided, 

 and that but one thread is formed from each mass; but the latter 

 conclusion is less certain than the former. In the dragon-fly, 

 Anax, the facts are similar, and in some respects still more clearly 

 shown. Stage b is shown in fig. 85 (the massive bodies all deeply 

 stained) ; and in fig. 86 (closely similar to Janssen's fig. 67 of the 

 spermatogonial prophases of Triton) are shown three nuclei lying 

 side by side, in which appear three successive stages of the unravel- 

 ling. The spiral disposition of the threads in this form is some- 

 times conspicuous, and may be clearly seen because of the tend- 

 ency of the chromatic masses to assume a peripheral position in 

 the nucleus. Not infrequently are seen nuclei like fig. 87 in 

 which a striking effect is given by the uncoiling threads. In such 

 cases it is very evident that the spirals are single, and the evi- 

 dence is strong that one thread is forming from each massive 

 body. 



These stages may be studied to still greater advantage in the 

 grasshoppers, where they have been accurately described and fig- 

 ured by Davis ('08). This observer describes the post-spermato- 

 gonial nuclei (Stage 6) as containing a series of elongated massive 

 bodies, very definitely polarized, approximately equal in number 

 to the spermatogonial autosomes, and having "approximately 

 the same orientation that the autosomes had during the preceding 

 telophases of the last spermatogonial division" (op. cit., p. 38). 

 In figs. 43 and 44 he represents the unravelling of a single thread 



