442 SUMMARY OF CURRENT RESEARCHES RELATING TO 



prolonged periods reduces the size of the yolk, and the effect persists for 

 weeks or months. 



J. V. Lawrence and 0. Riddle find that there are differences in the 

 fat and phosphorus metabolism of male-producino; and female-producing 

 ova. In the adult female the blood-plasma lis richer in alcohol-soluble 

 substance and phosphorus than in the adult male, and this increases 

 during sexual activity. The initial metabolic difference in the two 

 kinds of eggs thus persists in the organisms that develop therefrom. 



Breeding Habits of the Midwife-toad.* — G. A. Boulenger contrasts 

 some of Kammerer's statements on the breeding habits of Alytes 

 obstetricans with his own observations, which confirm on all important 

 points those of de I'lsle. Kammerer supports the old belief, originating 

 with Demours in the eighteenth century, that the male toad pulls out 

 the strings of eggs from the female, and thus performs an obstetric 

 function. But according to the author, and to de I'lsle, who witnessed 

 the whole process of parturition twenty-three times, the ova are expelled 

 suddenly, in a second or two, forming a ball-like mass between the hind- 

 legs of the couple, and the male does not attempt to disentangle the 

 strings until after about ten minutes' rest. According to the author's 

 observations there are two distinct phases in the operation, which he 

 observed seven times — the first, ending with the extrusion of the eggs, 

 during which the male clasps the female round the waist ; the second, 

 during Avhich the male clings to the neck of the female, and proceeds 

 with the fertilization and the movements of the hind limbs, by means 

 of which the eggs are entwined round them. Another discrepancy 

 between the results of the two investigators is in regard to ovi- 

 position in water. Kammerer says that if the eggs are laid in water 

 the gelatinous capsules swell up, and thus lose their viscosity. The 

 strings do not adhere in the normal manner to the hind-limbs of the 

 male, and therefore remain lying in the water, but, notwithstanding 

 this, some of the eggs develop. Boulenger's experience is different on 

 ])oth points. He finds that the eggs are normally subjected to consider- 

 able soaking with fluid from the bladder of the male during fecundation, 

 and the swelling when they are placed in water is not very much in- 

 creased, nor is the toughness and viscosity of the capsules diminished. 

 In very shallow water the male should be able to deal with the strings in 

 the usual way. Experiment showed that, if the eggs were left in water, 

 development did not proceed beyond the fifth day. Boulenger admits 

 that the great perfection to which Kammerer has brought his terra- 

 rium may account for his higher percentage of success in breeding, 

 but in view of the difference between the Viennese observer's results 

 and those of others — and, indeed, of the contradictoriness of some of 

 Kammerer's own statements — he suggests that careful revision is 

 necessary. 



In regard to Kammerer's claim to have observed a structural varia- 

 tion in the fourth generation of the " water-form " — a black nuptial 

 callosity on the " thumb " or inner finger — Boulenger quotes Bateson's 



* Ann. Mag. Nat. Hist., xx. (1917) pp. 173-84. 



