Hermaphroditism among the Apodidce. 305 



gradually with mere periodical swellings. May we not assume 

 that the failure to form tiie typical branchings indicates a 

 lack of nutrition, one result of whicii is that the cells which 

 here, under more favourable conditions, miglit have pro- 

 duced eggs, divide up into sperm-cells ? The evidence, 

 therefore, certainly points to a normal hermaphroditism 

 among the arctic Apodidse. With regard to the more 

 central European species, both the liermaphrodite specimens 

 of L. productus and of Apus cancriformis above described 

 were apparently suffering some privation in the way of 

 nourishment, if we may judge from the generally collapsed 

 condition of the immature eggs ; while, further, the con- 

 dition of tiie alimentary canal of the specimen of Apus cancri- 

 formis clearly indicates a state of semi-starvation. 



In these facts, then, it seems that we have some indications 

 of the conditions which induce hermaphroditism. It appears 

 that the Apodidte which, under favourable circumstances, 

 produce parthenogenetically, may become hermaphrodites 

 when food is scarce. Tiiis hermapliroditism is thus super- 

 imposed upon the parthenogenetic females. 



On comparing this with observations which have been 

 made on kindred forms, interesting speculations are suggested 

 as to the relations of these hermaphrodites to true males. 

 The males of different families of Cladocera begin to appear 

 when the year is waning and food is getting scarce. Kurz * 

 found that the males of Daphnia always appeared wlienever 

 the puddles began to dry up, and he even succeeded in some 

 cases in producing males artificially by slowly draining off 

 the water in which the animals lived. This observer, on 

 accidentally finding hermaphrodite specimens of four distinct 

 species just about the time when the males begin to appear, 

 suggested that such were probably of frequent occurrence and 

 that this might be a sort of provisional arrangement. The 

 needed males were not immediately forthcoming, and herma- 

 phroditism tided over the interval. 



Kerhervd's observations led to the same conclusion ; not 

 only do males appear on the advent of " hard times," but the 

 females undergo a change. " Quelques jours suffisent pour 

 transformer une Daphnie parth^nog^netique, indifferente aux 

 males en femelle ephippiale douee d'affection sexuelle, en 

 pondeuse d'oeufs destines a etre fecondes. Le facteur prin- 

 cipal de cette modification, ici je le repete, est la peuurie des 

 vivres " f. 



* Kurz, " Ueber Androgyne Missbildung bei Cladoceren,"' SB. Akad. 

 Wien, Ixix. Abtli. i. 1874, p. 40. 



t Mem. Soc. Zool. de France, v. p. 227 (1892). 



