ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 359 



of life about half that of the wild fly. and giving rise to a small number 

 of offspring. The hybrid offspring of low-producing truncates and 

 high-producing wild stocks arc high producers, and it makes little 

 difference whether the father or the mother is from the low-producing 

 truncate stock. Low production is transmitted through egg or sperm 

 to the grandchildren. The short life is a factor in the low production. 

 but there is more than that. There is incompatibility between the egg 

 and the sperm of the truncates, only one egg in every four or five 

 giving rise to an adult. It is suggested that the truncates have become 

 homozygous for many factors, and that the rise of fertility when crossed 

 into other races is to be explained on the assumption that ' ; the com- 

 bination formed is heterozygous for more characters upon which fertility 

 depends, and consequently more likely to develop." 



Fertility in Drosophila.* — Roscoe R. Hyde, continuing his inquiry 

 into fertility in Drosophila ampdophila, has made experiments bearing on 

 the question whether or not a rise in fertility will result when one strain 

 is crossed with another. In the crosses there is no sudden rise in 

 fertility, but, on the other hand, a peculiar relation exists in that the 

 stock in each case having the highest fertility is able on crossing to bring 

 the fertility of the lower stock up to its level, and this is true whether 

 through the male or through the female. High-producing stocks can 

 bring the fertility of low-producing stocks to their level whether 

 descended from the same or from different germ-plasms. Inbreeding- 

 does not seem to be the cause of low fertility, but low fertility is likely 

 to accompany close inbreeding, provided it is not guarded against by 

 rigorous selection. The author has also made experiments f bearing on 

 the effects on fertility of crossing within and without an inconstant 

 stock. 



Infertility of Rudimentary Winged Females of Drosophila 

 ampelophila.J— T. II . Morgan has examined the ovaries of many 

 rudimentary females of this fly. In the majority of cases the ovaries 

 become nearly as large as those in the normal female, and while they 

 may contain full-sized eggs, most of the eggs remain immature. Most 

 females lav no eggs. Sometimes a few are laid, and at least some of 

 these hatch. The experimental evidence goes to show that the in- 

 fertility is due, largely at any rate, to a retention of eggs, even after 

 copulation. The sterility cannot be supposed to be due to any 

 additional peculiarity that' has appeared in the rudimentary stock, but 

 must be one of the attributes of the factor for rudimentariness itself. 



Orienting Reaction of Blowfly Larva. § — Bradley M. Patten has 

 sought to make exact quantitative measurements of the light reactions 

 of the larvae of CaUiphora erythrocephala Meigen. The light was applied 

 as two opposed beams, the intensity of which could be easily controlled 



* Jouru. Exper. Zool., xvii. (191-1) pp. 343-55 (1 diagram). 

 f Journ. Exper. Zool., xvii. (1914) pp. 356-72 (11 diagrams). 

 X Amer. Nat., xlix. (1915) pp. 210-50 (2 figs. I. 

 & Journ. Exper. Zool., xvii. (l'Jll) pp. 213-SO (21 figs.). 



2 c 2 



