10 STUDIES ON THE GERM CELLS OF APHIDS. 



The Goldenrod Aphids. 



The goldenrods, besides serving as hosts for several beetles, offer to 

 the insect collector at least two distinct species of aphids. On the 

 beach goldenrod are large numbers of dark brown aphids with green 

 males. The sexual forms were found at Woods Hole on September 

 27. The polar body (pb) and the segmentation nucleus of the par- 

 thenogenetic egg are shown in figures 79 a and 79 b, the metaphase 

 of the first spermatocyte in figures 80 and 81, one daughter plate of a 

 late anaphase in figure 82, the metaphase of the second spermatocyte 

 in figure 83, and one of the daughter plates of an anaphase in figure 

 84. In this species four of the chromosomes are of nearly the same 

 form and size, the other two being very much smaller and one 

 slightly smaller than the other. This was the first aphid in which 

 both male and female embryos were found in sections of the same 

 individual. This was quite unexpected, as in the forms studied last 

 year, particularly the Oenothera aphid and the migratory rose aphid, 

 the male and female sexual generations seemed to be entirely separate, 

 the former from apterous, the latter from winged mothers. 



The tall goldenrod, Solidago altissima, is the host of quite a differ- 

 ent aphid with the same number of chromosomes. The ordinary 

 parthenogenetic individuals and the sexual females are green, the 

 males red, and the mothers of the sexual generation either green or 

 red, individuals of both colors giving rise to both male and female 

 progeny. Figures 85 and 86 are prophases of the first spermatocyte 

 mitosis, figure 85 before the pairing of the chromosome and figure 86 

 during that process. Figure 87 is the metaphase and figure 88 an 

 early anaphase of the first spermatocyte from material fixed with Gil- 

 son 's fluid, figures 89 and 90 from Flemming material. Figures 91 

 and 92 are the metaphase of the second spermatocyte. The chromo- 

 somes, though the same in number, will be seen to differ considerably 

 from those of the brown goldenrod aphid in both form and size. 



The Clover, Birch, and Beech Aphids. 



On the paper birch were found the sexual forms of a brown aphid. 

 Most of the males were too old to be of use and there were no parthen- 

 ogenetic forms when they were discovered late in October. Only 

 one drawing of the first spermatocyte, showing nine chromosomes, 

 was made from an aceto -carmine preparation (fig. 93). Only a few 

 young males of the clover aphid were obtained. The testes of these 

 showed a characteristic metaphase of the first spermatocyte contain- 

 ing one large chromosome surrounded by a circle of seven nearly 



