ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 445 



upon the female, and a retarding influence upon the male, as regards 

 sexual development. 



Fertility and Age.* — Raymond Pearl notes that in a variety of 

 mammals the rate of fertility, starting at a low point, at the beginning 

 of the sexual life, rises with advancing age to a maximum, and then 

 declines with further increase in age, until total sterility is reached. In 

 the domestic fowl he finds that there is a decline in net reproductive 

 ability or fertility, as measured by the reproductive index, with advanc- 

 ing age in both sexes. The rate of the decline, however, is more rapid 

 in the male than in the female. As contrasted with what is noted for 

 mammals, there is a steady and progressive decline in fertility after the 

 first breeding season. "There is a significant drop in reproductive 

 ability as we pass from a combined age of two years for the mated 

 birds to three years. In passing from three years to four there is no 

 significant change in reproductive ability. In passing from a combined 

 age of four years to that of five years, there is a large drop in the net 

 reproductive ability of the mating." 



Superfetation and Deferred Fertilization among Mice.t — F. B. 



Sumner, working with Peromyscus maniculatus, has made some interest- 

 ing observations which point, with considerable probability, to two 

 facts : (1) to a defijiite periodicity in ovulation, continuing in some 

 cases throughout pregnancy ; and (2), with even greater probability, to 

 the retention by the spermatozoa of their fertilizing power for days, or 

 even weeks, after reception into the uterus or fallopian tubes. The 

 phenomena do not seem to be very rare. Most of the supernumerary 

 litters comprised normally healthy animals. In four cases out of eight 

 the parents of the supernumerary litters were both very young mice. The 

 possibility suggests itself that some of the alleged cases of " telegony " 

 may be due to the retention of spermatozoa received from an earlier mate. 

 A later copulation with a different partner might happen to coincide 

 with a conception in which the earlier insemination was really the 

 effective one. 



Correlation of Internal Secretion and Female Sex Functions.^ 

 W. Blair Bell has given a connected account of recent work by himself 

 and others which goes to show that the reproductive functions are 

 directed and controlled by all the organs of internal secretion acting 

 together. The ovaries are to be considered as part of a system, to 

 which most, if not all, the other endocritic (or ductless) glands belong, 

 and in which these other organs in their relation to the reproductive 

 functions figure with as great importance as the ovaries themselves. 

 Besides producing ova, the ovaries produce an internal secretion or 

 internal secretions, not yet isolated. The evidence rests upon the 

 results of extirpation, destruction, and implantation experiments, and 



* Proc. Nat. Acad. Sci., U.S.A., iii. (1917) pp. 354-6. 



+ Biol. Bull., XXX. (1916) pp. 271-85. 



; The Sex Complex. London : 1916, xvii and 933 pp. (50 figs.). 



