154 CHAS. W. METZ AXD JOSE F. XOXIDEZ. 



The testes of Lasiopogon resemble those of Asilus and many 

 other members of the Asilidae, in being a pair of long, coiled tubes, 

 with the spermatogonia near the apex, and successive stages in 

 spermatocyte development progressing in serial order toward the 

 base. This serial orientation of stages makes it relatively easy to 

 follow the succession of events during spermatogenesis. 



SPERMATOGONIA. 



At the extreme tip of the testis lies a small mass of disorgan- 

 ized, nutritive material containing only a few cells. Adjacent 

 to this lie the spermatogonia, many of which are connected with 

 the nutritive mass by long protoplasmic processes. This con- 

 dition differs from that in many other asilids. In the latter the 

 nutritive mass lies in the center of the tube, a short distance from 

 the end, and is surrounded on all sides by spermatogonia. 



The spermatogonia present no unusual features except in late 

 prophase. There the nuclei appear to undergo a change similar 

 to that observed in the primary spermatocytes. The nuclear 

 membrane breaks down or becomes irregular in outline and the 

 chromosomes appear to lie free in the cytoplasm, each surrounded 

 by a hyaline zone of about the thickness of the chromosome. The 

 other stages in spermatogonial development appear to be essen- 

 tially the same as those in Asilus sericeus (Metz and Nonidez, '21). 



The spermatogonial chromosome group probably consists of 

 six pairs, or possibly of five pairs of autosomes and an unpaired X- 

 chromosome. Fig. I only shows five pairs, but the nucleus may 

 not be entire. One or two other figures (not suitable for drawing) 

 seem to include six pairs, and spermatocyte metaphases almost 

 certainly include six chromosomes (e.g., Fig. 12). 



THE GROWTH PERIOD. 



Owing to the scarcity of final spermatogonial division figures 

 and to the fact that the final spermatogonia are not readily iden- 

 tified by size differences, as they are in some asilids, it is difficult 

 to detect the boundary between spermatogonia and spermato- 

 cytes. However, the earliest growth stages seem to repeat the 

 spermatogonial prophase changes, as in the case of Asilus sericeus 

 (1. c., p. 171); and so far as we can determine they show essen- 



