Studies on Chromosomes 37 



oocytes and the great preponderance of constructive activity in 

 these cells; and it is especially this coincidence that leads me to 

 the general surmise that one of the important physiological 

 differences (I do not say the only one), between the chromosome- 

 groups of the two sexes, may be one of constructive activity. 

 I have elsewhere (The Cell, Chapter VII) reviewed at some 

 length the evidence pointing toward the conclusion that the 

 nucleus (more specifically, the chromatin) is especially concerned 

 with the constructive processes of cell metabolism; and while I no 

 longer hold the view that the nucleus can be considered as the 

 actual formative center of the cell, it still seems to me very 

 probable that the formative processes are directly or indirectly 

 under its control, as has been advocated by many students of 

 cell-physiology. If this view be well-founded, the facts observed 

 in Hemiptera give a very definite and concrete basis for assuming 

 a greater constructive activity in the cells of the female generally, 

 which reaches a climax in the growth-period of the oocyte. 1 It 

 seems possible that some of the specific differentiations that take 

 place in the later history of the germ-cells may be directly trace- 

 able to the primary difference in the growth-process. It is well 

 known that the young oocytes and spermatocytes show a very 

 close similarity, not only in size but also in many details of struc- 

 ture. The enormous accumulation of cytoplasm in the oocyte 

 as compared with the spermatocyte leaves the latter with a great 

 relative excess of the kinoplasmic or archoplasmic material in which 

 the most characteristic differentiations of the spermatozoa such as 

 the acrosome, middle-piece, axial filament and tail-envelopes 

 take their origin. Perhaps a direct causal relation here exists. 



'This suggestion recalls the theory developed by Geddes and Thomson, in their well known work on 

 the "Evolution of Sex," that " the female is the outcome and expression of relatively preponderant anabo- 

 lism, and the male of relatively preponderant katabolism" (pp. cit., revised ed., 1901, p. 140). As de- 

 deloped by these authors, this theory has always seemed to me to have too vague and general a character 

 to have much practical value, though it expresses a certain physiological contrast between the sexes that 

 undoubtedly exists. My suggestion is only remotely connected with that theory, since it refers the differ- 

 entiation of the sexes to a functional difference that preexists in the cells of the male, and involves no 

 contrasted processes of anabolism and katabolism. Nevertheless, the observations here brought forward 

 may harmonize with that side of the theory which lays stress on the preponderant constructive activity of 

 the female cells. 



