402 EDMUND B. WILSON 



the spermatogonia! autosomes. In some at least of the objects 

 I have examined these threads are single, not double; and I can 

 find no evidence that they consist or have consisted of two inter- 

 lacing spirals or closely associated halves. In this respect they 

 seem to be quite like the spirals that uncoil from massive bodies 

 in the spermatogonial prophases in Phrynotettix. In this case 

 I can speak with complete assurance ; for the evidence afforded by 

 McClung's brilliant preparations of this form is absolutely demon- 

 strative that the spirals are single, and that the longitudinal dual- 

 ity is produced by a subsequent longitudinal split of the spiral 

 thread (which is essentially in agreement with Janssens's earlier 

 conclusions in the case of Triton). 



For the foregoing reasons I accept the probability that the 

 parallel union of leptotene-threads does not form part of a pecu- 

 liarly modified process of longitudinal division, but should be 

 regarded as a true conjugation or parasynapsis of entire chromo- 

 somes. Apart from the convincing evidence afforded by the 

 sex-chromosomes, my observations are essentially in agreement 

 with those of the Schreiners in regard to the origin of the lepto- 

 tene-threads. These observers describe the latter in Tomop- 

 teris as arising from much thicker, loose, polarized loops of the 

 diploid number (18) which transform themselves into convoluted 

 threads in a manner somewhat similar to that seen in the insects : 

 "Nicht selten haben wir Bilder gesehen, die uns den Eindruck 

 gegeben haben, dass das Chromatin der lockeren Schlingen sich 

 zuerst zu einem unregelmassig aufgebauten, stark gewundenen 

 und gefalteten Bande sammelt, aus dem wieder die deutlich 

 begrenzten diinnen Faden hervorgehen" ('06, p. 18). Later, 

 "Die Chromatinfadchen, die auf Stadien wie Fig. 18 und 20a 

 hervortreten sind, vovon uns fortgesetzte Untersuchungen immer 

 fester iinberzeugt haben, in den breiten aufgelockerten Chro- 

 matinbander der vorgehenden Stadien spiral aufgerollt oder zusam- 

 mengefaltet sind" ('08, p. 10, italics mine). My own study of 

 the Tomopteris slides gives me the same impression; and I think 

 it probable that the phenomenon here seen is of the same nature 

 as that which so clearly appears in the insects, though the thick 

 'Chromatinbander' are here much less sharply defined. Jans- 



