, 34 w - s - SUTTON. 



mosome series which forms the chromatic portion of the sperm - 

 head and consequently is to be regarded a priori as the series 

 which will reappear in the sperm-nucleus in the act of fertilization. 

 If this is true --and everything speaks for and nothing definitely 

 against the correctness of the assumption then the conclusion 

 seems unavoidable that the mate to each of the eleven chromo- 

 somes must be furnished by the egg-nucleus to produce the eleven 

 pairs characteristic of all the early germ-cells, of the follicle-cells 

 of the ovary as shown by Fig. n, and probably also of the 

 ordinary somatic cells.' 



To sum up, in Brachystola the nuclei, not only of the pre- 

 synaptic germ-cells, but also of cells which have been shunted off 

 from the germinal cycle, are characterized by the possession of a 

 chromosome group made up of two morphologically equivalent 

 series of eleven members each. 2 Comparison shows that the 

 size-relations between various members of these series are ap- 

 proximately the same in different nuclei of the same or different 

 cell generations. The numerical reduction (pseudo-reduction) is 

 accomplished by the union of homologous members of the two 

 series of a nucleus, and this union is terminated in the second 

 spermatocyte division by the separation of the daughter-chromo- 

 somes of the original conjoints at their point of union and their 

 passage to opposite poles. We are virtually able to recognize 

 each chromosome in eleven consecutive cell-generations ; and in 

 the prophases and telophases of nine of these, the chromosomes 

 are separated from one another for a great part of their length, 

 only their polar ends lying in the common chamber. No con- 

 tinuous spireme is formed ; .and although after each division there 

 is a brief interval, during which chromosomic boundaries can no 

 longer be traced, the regular correspondence, unit for unit, of the 

 mother series with the daughter series establishes a high proba- 

 bility that we are dealing with morphologically distinct individuals, 

 each of which bears to its mother element a genetic relation 



1 Cases of cells other than germ-cells in which an accurate count of the chromo- 

 somes is possible are extremely rare on account of the crowded condition of their 

 nuclei ; but I am able to state that in the cells of the ovarian follicles and of the com- 

 mon collecting ducts of the testes every division figure shows large and small 

 chromosomes in apparently the same relation as those found in the spermatogonia. 



2 Besides the accessory chromosome. 



