3S8 EDMUND B. WTLSON 



to be entirely wanting in these insects, where in its place we find 

 the closely convoluted and apparently non-polarized synaptic 

 knot or synizesis. The controversy as to whether the latter is an 

 artifact, due to the coagulating effect of the reagents, seems to 

 be terminated by the fact, determined by Sargant ('97), Overton 

 ('05), Berghs ('04), Oettinger ('09), and myself ('09 a, '09 b) 

 that the synizesis may be clearly seen in the fresh (living?) mate- 

 rial immediately after gentle teasing apart of the cells in a nor- 

 mal fluid (Ringer's solution) in which the spermatozoa continue 

 actively to swim. Neither at this stage nor in those that imme- 

 diately precede or follow is there the least sign in these animals 

 of an elongation of the sex-chromosomes or of a giving off of 

 nuclear material to the protoplasm. 



Third, in Tomopteris and Batracoseps the pachytene-loops 

 formed in synapsis persist as such throughout a large part of the 

 growth-period, without undergoing at any period an apparent 

 loss of identity in a 'diffuse' stage such as is so characteristic of the 

 Hemiptera. In Batracoseps the pachytene-loops become longi- 

 tudinally divided ('diplotene') near the end of the growth-period, 

 when they give rise directly to the prophase-figures. In Tomop- 

 teris the diplotene-threads are apparent at a much earlier period 

 (Schreiner), but here too give rise directly to the prophase-figures. 

 In the Hemiptera here considered the diplotene is likewise 

 formed very early, but the diffuse stage is interpolated between it 

 and the definitive formation of the prophase-figures, and the 

 greater part of the growth-period is passed in this condition (in 

 some cases accompanied by a second contraction-figure in the 

 later period). There is, however, an analogy in this respect 

 between these Hemiptera and Tomopteris, where the Schreiners 

 describe and figure ('06, p. 19, figs. 31, 32) a stage following the 

 early diplotene in which the parallel halves of the double threads 

 become longer, thinner, less regular, and spread more or less widely 

 apart, though still retaining their connection at certain points. 

 It is very probable that this process corresponds to that which 

 marks the beginning of the diffuse stage in the Hemiptera, but 

 does not proceed so far; and that in this respect Tomopteris is 

 intermediate between these animals and the Amphibia. Perhaps 



