SPERMATOGENESIS OF APHIDS. 357 



suitable for the purpose of studying the spermatocyte divisions. 

 As is the case in other aphid's, the primary spermatocytes of these 

 aphids divide unequally, and the anaphase shows the lagging chro- 

 mosomes. I have found in these aphids telophases of the second 

 maturation division of the smaller secondary spermatocyte, but 

 have observed no developing smaller spermatid ; we may, there- 

 fore, conclude that the smaller secondary spermatocytes and the 

 smaller spermatids of these aphids degenerate as in the cases of 

 the aphids studied by Morgan, von Baehr and Stevens. In Ma- 

 crosiphnni ambrosia I observed cases in which all smaller sec- 

 ondary spermatocytes seemed to be dividing, but I will conclude 

 in a succeeding paper whether all the smaller secondary sper- 

 matocytes divide or not. 



In the cyst, where larger spermatids are already attached to the 

 sustentacular cells, there are seen spermatids which look like the 

 smaller spermatids of Stomaphis yanois. As stated above, since 

 no development of the smaller spermatids was observed, they 

 must be larger spermatids. In slightly younger cysts some sper- 

 matids are seen among the developed tails of other larger sper- 

 matids, which are about to attach to the sustentacular cells. Such 

 spermatids probably have no chance of reaching the cells. I have 

 found cases in which the larger spermatids are already attached 

 to the cells, but some spermatids are seen among the ends of the 

 tails of the larger spermatids. In other cysts spermatids with 

 condensed nuclei are seen apart from the sustentacular cells, 

 while others are attached to them. 



As in the case of Stomaphis yanois young spermatids of these 

 aphids change their orientation to the same direction ; some sper- 

 matids, therefore, move to the sustentacular cells across the whole 

 diameter of the cyst or reach the cells moving along the epi- 

 thelium. If they move to the sustentacular cells along the epi- 

 thelium, as most of the spermatids do, they may lose the chance 

 to become attached to them. Developed spermatids have been 

 found by the side of spermatids which are attached to the sus- 

 tentacular cells and are developing. They w r ere probably pre- 

 vented from reaching the cells by other spermatids, and their 

 development came to a standstill ; they, consequently, show 

 younger stages than the spermatids which are attached to the 



