230 MICHAEL F. GUYER. 



mosome or group of chromosomes to sex is merely a quanti- 

 tative one, the female type resulting when a greater amount of 

 active chromatin is present. Extensive bibliographies will be 

 found in the recent papers of Wilson ('05, '06, '09), Payne ('09), 

 Morse ('09) and Morgan ('10). 



In conclusion I wish merely to point out that as regards ac- 

 cessory chromosomes, conditions prevail among vertebrates 

 (guinea, chicken, rat, man, etc.) similar to those found among 

 numerous Tracheata (and probably certain other invertebrates) 

 where the accessories are undoubtedly associated in some way 

 with the phenomena of sexuality. In Syromastes (Wilson, '096), 

 which seems to parallel most nearly the condition found in man, 

 half of the spermatids were found to possess two more chro- 

 mosomes than the remainder. It was predicted by Wilson 

 that in consequence the somatic cells of the female of this species 

 would show two more chromosomes than the somatic cells of 

 the male. Later the facts were found to be in exact accord 

 with his prediction, the somatic cells of the female containing 

 twenty-four, of the male twenty-two chromosomes. Similar 

 verifications have been made in other tracheate forms. 



In the light of these facts we should expect the somatic cells 

 of man to contain twenty-two, and of woman, twenty-four 

 chromosomes. The tissues of the female have not yet been 

 studied with this in mind. Flemming ('97) records the somatic 

 number of chromosomes, determined from corneal cells, as twenty- 

 four but unfortunately he does not record the sex of the sub- 

 jects from which the material was obtained. If it were a female 

 his count would bear out the interpretation given above. 



SUMMARY. 



1. Twenty-two chromosomes differing considerably in size 

 occur in all spermatogonia in which a definite count could be 

 made. In a few instances two, apparently the two accessory 

 chromosomes, were seen considerably to one side of the main 

 mass of chromosomes, surrounded by a small clear court of 

 cytoplasm. 



2. Twelve chromosomes appear for division in the primary 

 spermatocyte, of which ten are evidently bivalent and two 

 accessories. 



