spermatogenesis 49 1 



chromosome, rather than the chromatin nucleolus of the other 

 Membracid.ie studied. 



Enchenopa binotata 



Enchenopa binotata was found throughout July at Cold Spring 

 Harbor on the locust and wild cherry trees, on blackberry bushes 

 and sometimes in general sweepings of weeds. Its spermato- 

 genesis has been the most puzzling of any form studied and the 

 following account is given tentatively, with the intention of going 

 over the work as soon as more material can be obtained. The 

 first facts to be noticed are that all the chromosomes appear as 

 dumb-bells in the metakinesis of the first spermatocyte (Fig. 128), 

 there is no lagging chromosome in the anaphase (Fig. 130), and all 

 the second spermatocytes have 10 chromosomes (Fig. 131), the 

 same number as the first spermatocytes. In iron haematoxylin 

 preparations extracted to the same degree as in other material, 

 no darkly-staining body appears in the rest stage, but in those 

 extracted for a shorter time, a long twisted body appears against 

 the pale spireme (Fig. 124). This can occasionally be traced into 

 a stage where the spireme has segmented (Fig. 125), but never 

 any further, as it does not assume a compact rounded shape until 

 the other chromosomes become condensed. The question arises 

 as to whether this body in the growth stage represents two sper- 

 matogonial chromosomes and consequently divides in both sper- 

 matocyte divisions as all bivalent chromosomes do; or whether 

 it is univalent, analogous to most odd chromosomes in insects, but 

 divides in the first spermatocyte division and not in the second, 

 thus differing from all the other Hemiptera Homoptera studied 

 and resembling most of the Heteroptera. There were a few sper- 

 matogonial plates in such a stage that it was possible to count 

 the chromosomes, but these did not have the chromosomes as 

 clearly spread apart as in most the other species studied. In five 

 plates, 19 chromosomes were counted (Fig. 123) and in two, 20. 

 One of those with 20 may, however, be deceptive; two of the chro- 

 mosomes are much smaller than any in the other plates, the plate 

 is at the surface of the section, and as x in Fig. 123 is V-shaped, it is 

 possible that the bend of the V was cut off" and the two small chro- 



