634 THE PHYSIOLOGY OF REPRODUCTION 



in this and other forms the female and not the male contains 

 an additional chromosome in its somatic cells. It is almost 

 certain also that the ova have one more chromosome than one 

 half of the sperms have, and the same number as that possessed 

 by the sperms which contain the additional chromosome. 

 Consequently the latter are supposed to produce females and 

 the former males. 



For example, in Anasa tristis the somatic cells of the male 

 contain twenty-one chromosomes, whereas those of the female 

 contain twenty- two. Half of the spermatozoa are supposed to 

 contain eleven chromosomes, the other half having only ten. 

 The ova are beheved to all resemble one another in containing 

 eleven chromosomes. It is concluded, therefore, that the 

 spermatozoa possessing the smaller number give rise to 

 males, while those with eleven chromosomes produce females.^ 



Payne ^ has recently shown that in Galgulus oculatus there 

 are two sorts of spermatozoa possessing respectively sixteen 

 and nineteen chromosomes, whereas the eggs are uniform in 

 containing nineteen chromosomes. Furthermore, the females 

 are beheved to have three more chromosomes than the males 

 {i.e. thirty-eight as compared with thirty-five). It is evident 

 therefore that the sexual differences of the chromosomes, even 

 in the same order of animals, do not conform to a single 

 numerical rule, but at present it would appear that where there 

 is a difference in the number it is always the female which has 

 more chrornosomes than the male. 



That two sorts of spermatozoa (one with an additional 

 chromosome) may exist in other animals besides insects has 



Publications, Washington. In these papers dimorphic spermatozoa (one kind 

 containing one smaller chromosome or lacking one chromosome) are described 

 for various species of Orthoptera, Coleoptera, Hemiptera and Lepidoptera. 



1 Miss Foote and Strobell (" A Study of Chromosomes in the Spermato- 

 genesis of Anasa tristis," Amer. Jour, of Anat., vol. vii., 1907), as a result 

 of an investigation with smear preparations instead of sections, find no evidence 

 of a persisting accessory chromosome in Anasa tristis, and believe that the 

 body described as such by Wilson is a plasmosome and not a chromosome. 



^ Payne, " On the Sexual Differences in the Chromosome Groups in 

 Galgulus oculatus," Biol. Bull., vol. xiv., 1908. Correns also has shown that 

 in some plants there are two classes of male germ cells, and that these are 

 produced in equal numbers (Die Bestimmung und Vererbung des Geschlechtes 

 nach neuen VersucJien mit hoheren Pjkmzen, Berlin, 1907). 



