February 14, 1913] 



SCIENCE 



271 



any X-element in the male, suggests very forcibly 

 that sex-chromosomes are present in all mammals, 

 generally in the male, exceptionally in the female. 

 The same end would be attained, that of numerical 

 sex-equality, whether present in the one or the 

 other sex. If this hypothesis can be further sus- 

 tained, it would seem cogently to reinforce the 

 evidence for an essential sex-determining function 

 of heterochromosomes. Interpreted in terms of 

 Mendelian heredity-formula;, in those mammals in 

 which an X-element is present in the male, the 

 female sex is homozygous, the male heterozygous. 

 The facts would seem to fit the hypothesis that 

 the accessory chromosome acts as a deterrent to 

 the development of maleness; or more accurately, 

 and in keeping with a quantitative interpretation 

 of sex in the last analysis, the accessory with its 

 egg-homologue (two X-elements) inhibits male 

 sex development; the single egg-homologue in 

 males being insufficient to counteract the male 

 tendency, thus giving origin to male individuals. 

 The complete paper will appear in a Carnegie 

 Institution publication. 



A. W. Meyer (Stanford University) : Observa- 

 tions on Giant Cells in Hemal Nodes and Acces- 

 sory Spleens. 

 M. F. GUYER (University of Wisconsin) : Semarks 

 on the "X" Element in Fowls. (Demonstra- 

 tion.) 



A reexamination of old material and a further 

 study of new material from the Langshan cock 

 abundantly confirms the original finding of an 

 accessory chromosome which passes undivided to 

 one pole of the spindle in the division of the 

 primary spermatocyte. The element in question 

 was demonstrated through the microscope to mem- 

 bers of the society. 



T. S. Painter (introduced by A. Petrunke- 

 vitch) : Spermaiogenesis in Spiders. 

 A cytologieal difference has been found in the 

 spermatogenesis of the dimorphic males of the 

 jumping spider, Mwvia vittata. The "gray va- 

 riety ' ' contains two supernumerary chromosomes 

 which do not divide in the last spermatogonial 

 division. During the first maturation division 

 these bodies show a definite association for the 

 accessory chromosome and pass with the latter to 

 one pole of the cell at this time. For this reason 

 these supernumeraries have been called "cteto- 

 somes" (implying, are the property of, are asso- 

 ciated with, some other body). During the second 

 maturation division the accessory chromosome 

 divides, but this could not be certainly deter- 



mined for the ' ' ctetosomes. " As a result of the 

 unequal spermatogonial division the sperm are of 

 three types: (1) sperm which bear the accessory 

 chromosome and "ctetosomes"; (2) sperm which 

 bear the accessory chromosome only; (3) sperm 

 which bear neither of these elements. 



The "tufted variety" of male lacks the "cteto- 

 somes" although a supernumerary chromosome 

 may be present. This body shows no relation for 

 the accessory chromosome and seems to follow no 

 definite law of distribution. Hence it was called 

 a "planosome" (indicating that it wandered 

 through the cell mitoses). 



' ' Planosomes ' ' have been found in many fam- 

 ilies of spiders. Most abundant in Amaurobius 

 sylvestri-s, which may carry as many as seven 

 "planosomes" and three "ctetosomes." 



The females of Mwvia vittata carry two doses 

 of the accessory element. 

 G. L. Kite (introduced by Oscar Eiddle) : 



Studies on the Physical Properties of the Struc- 

 tural Components of Protoplasm. 

 Mary T. Harmon (introduced by J. W. Scott) : 



The Character of Cell Division in the Sex Cells 



of Taenia teniceformis. 



GENETICS 



H. H. Newman (University of Chicago) : Five 



Generations of Congenital Night-blindness in 



an American Family. 



During the past two years the writer, in colabo- 

 ration with Miss E. L. Brown, a former student 

 of his and a member of the affected family, has 

 obtained data concerning 76 individuals belonging 

 to a family connection showing a peculiar type of 

 hereditary night-blindness. The family originated 

 in North Carolina, but now resides in Texas. The 

 defect is present through life and is usually, 

 though not always, associated with myopia and 

 strabismus. This complex of optic affections is 

 inherited from affected men through unaffected 

 daughters to some of the grandsons, and in no 

 other way. Thus, as in the case of color-blind- 

 ness, the character gains expression only in alter- 

 nate generations. The mechanism underlying this 

 mode of inheritance is probably closely allied to 

 that described by E. B. Wilson as underlying the 

 nheritance of white eyes in Drosophila.^ Accord- 

 ng to this scheme the factor for night-blindness 

 s contained in the X chromosome, which Guyer 

 has described for man. Frequently associated 

 with night-blindness, but neither sex-limited nor 



= See Journ. Morph., Vol. 22, No. 1, p. 96. 



