132 SUMMARY OF CURRENT RESEARCHES RELATING TO 



it nowise receives contributions of cells from the ectoderm. It seems 

 clear that the duct is not developed from an ectodermic groove. If the 

 nephridia of Vertebrates ever opened to the surface through ectodermic 

 pores, and later into a canal arising from the ectoderm, ontogeny has 

 failed to repeat phylogeny in Acanthias, for there is no hint of such a 

 condition in the development. 



Experiments on Amphibian Ova.* — R. A. Gortner and A. M, Banta 



have tried the effect of dilute solutions of certain phenolic compounds on 

 eggs of Amphibians, with particular reference to pigmentation and 

 toxicity. It seems that black melanic pigment results from the inter- 

 action of an oxidizing enzyme of the tyrosinase type with some oxidiz- 

 able chromogen, the exact nature of which has not been ascertained. 

 Gortner has shown that w-di-hydroxyphenols inhibit the action of 

 tyrosinase in vitro, and it is suggested that certain types of colourless 

 animals owe their lack of pigment to the presence of inhibitory com- 

 pounds. Gortner and Banta find that orcinol in 0* 05-0* 01 p.c. 

 concentration produces retardation in growth and considerable retarda- 

 tion in pigment development. Resorcinol is even more effective. 

 Tyrosin is, at most, only slightly toxic at saturation (0*04 p.c). 

 Bacterial infections are very common and make the solution sufficiently 

 toxic to slightly retard development and occasionally reduce pigmentation. 

 In most cases a marked increase in pigmentation occurred when the 

 embryos were kept in solution of tyrosin of - 01-0 "04 p.c. con- 

 centration during and after the onset of pigmentation. To give one 

 other example, tyrosol in concentration as great as * 05 p.c. retarded 

 growth and pigmentation, and killed Spelerpes larva? within 15 days. 

 Weaker solution retarded growth and pigmentation, but did not prove 

 fatal, and in time the animals developed the usual amount of pigment. 



Sex Ratio among Jews. f— Raymond Pearl and R. N. Salaman dis- 

 cuss the possible connexion between the time of the fertilization of 

 the ovum and the sex ratio. The sex ratio among Jews sometimes shows 

 a marked preponderance of males, e.g. among Russian Jews, 1459 per 

 thousand in 1893, 1331 in 1897, 1295 in 1901. It may be that there 

 is negligence in recording the births of daughters. Pearl and Salaman 

 have enquired into a possible connexion with the time of fertilization 

 of the ovum relative to the catamenial period (very strictly fenced off 

 by Jewish regulations), and find no evidence of this. The higher male 

 sex-ratio shown by the general Jewish statistics, if not due to faulty 

 registration, must owe its origin to other factors than the time of the 

 fertilization of the egg. The results leave open the question of the 

 possible importance of the metabolic condition of the germ-cells at the 

 time of fertilization. The distribution of ovulation over the inter- 

 menstrual period in the human female is so wide as to preclude any 

 possibility of forming any judgment as to the relative age of discharged 

 ova, on the basis of the time of menstruation. 



* Biochemical Bulletin, iii. (1914) pp. 357-6S. 

 t Amer. Anthropologist, xv. (1913) pp. 668-74. 



