MALE AND FEMALE EGGS OF PHYLLOXERANS. 205 



as has been stated above, the whole number ; and this is true for 

 the somatic cells of both male and female embryos. In the sper- 

 matogonial cells the whole number of chromosomes is present, 

 but in the two following spermatocyte divisions the half, or re- 

 duced number, occurs. I have seen the spindle in one winter 

 egg, which seems to have only the half-number of chromosomes. 

 It is evident, therefore, that the complete number of chromo- 

 somes is characteristic both for somatic and germinal cells 

 throughout the life cycle, except for the winter egg and the sper- 

 matocytes, where the reduced number occurs preparatory to fer- 

 tilization. After fertilization the number % of the chromosomes 

 would be the same as the whole number. Thus it is evident 

 that there is no reduction in the number of the chromosomes in 

 the parthenogenetic egg, but there is in the winter egg. The 

 former is not, the latter is, fertilized. The results for Phylloxera 

 are in these regards parallel to those that Stevens has recently 

 obtained in the aphids. 



The Cytoplasm of the Male and Female Eggs. Since no 

 discernible difference was detected between the chromosomes of 

 the small male and the larger female eggs, I examined with some 

 care the cytoplasm of these two kinds of eggs. In the male 

 eggs there is less yolk and the center of the eggs is occupied by 

 a clear mass of cytoplasm, while in the female egg there is more 

 yolk and no central cytoplasm. I have not observed any other 

 differences, and even those just noted can not be made out with 

 certainty for all eggs, but represent the extremes of the series. 

 Double and triple stains gave no differences. that I could detect. 

 In the ovaries the eggs showed no differences. In Dinophilus, 

 according to Richard Hertwig, the large female eggs are formed 

 by the union of several cells. It would be difficult to detect such 

 a difference if it existed in the case of Phylloxera, since the ovarian 

 eggs appear to be fused together at their inner ends, and each egg 

 as it leaves the ovary remains attached by a cord of protoplasm 

 to the fused center of the egg-mass. 



There are striking differences in the development of the male 

 and the female embryos, and these I have followed in some detail, 

 but can not present the results at this time. One important dif- 

 ference must however be alluded to, namely, the precocious 



