564 4. Fortpflanzungslehre. 



The author confirms and amplifies the observations of Maupas (1900) 

 on Rh ab ditis and Diplogaster. Maupas found that the species of these 

 genera füll iuto three categories (1) Bisexual species; (2) Hermaphrodite species 

 in which the majority of individuals are protandrous and self-fertilising, but 

 among them occur a few male individuals, which though apparontly perfectly 

 developed, take no part in reproduction. (3) Parthenogenetic species in which 

 males have not been found. 



It is supposed that the hermaphrodite forms are derived from the bisexual 

 by the production of sperniatozoa in the ovary, and in species in which her- 

 maphroditism is incipient, as indicated by the occasional occurrence of pure 

 females, or by the production of sperniatozoa in only part of the gonad, a 

 higher proportion of males occurs than in species with more advanced herma- 

 phroditism. 



Most of these results are confinned by Potts. In Diplogaster mau- 

 pasi residual males are more numerous than in any known species, reaching 

 30 per cent. Their secondary sexual characters are very variable. Apparently 

 normal and functional spermatozoa are produced, but copulation never takes 

 place. The production of males is cyclical; a few generations in which males 

 are frequent alternate with periods in which only hermaphrodites are produced. 

 No rule could be discovered geverning the causes of fluctuation in male pro- 

 duction. The production of males from a Single worm varies very widely in 

 different batches of eggs. Even when males were most frequent there was no 

 tendency to find female or partially hermaphrodite individuals. Tliis differs 

 from the conclusions of Maupas in Rh ab ditis. 



In Rhabditis gurneyi the formation of spermatozoa is not confined 

 to the anterior end of the gonad, but occurs at any part and at any time 

 throughout maturity. Frequently sterile eggs are laid at the onset of matu- 

 rity from the retarded production of spermatozoa. No males were found in 

 this species, which is thus more completely hermaphrodite than in other known 

 free-living species. 



Diplogaster maupasi was bred by self-fertilisation for forty-six gene- 

 rations with no deterioration. They were reared in drop-cultures of peptone 

 Solution, allowed to putrify tili cloudy with bacteria. In sterile Solutions 

 growth is suspended and few eggs are laid, bnt in Solutions containing bac- 

 teria eggs develop to maturity in four days. The Optimum temperature is 

 19° to 25° C; at 30° C the animals died and at 26° re 28° fertile eggs were 

 not produced. 



In conclusion the author discusses the nature of the hermaphroditism in 

 Nematoda, and the occurrence of self-fertilisation among animals. He quotes 

 Zur Strassen's evidence that in Bradynema it is apparently the male larvae 

 which develop into hermaphrodites, which suggests that within the Nematoda 

 in some forms hermaphrodites are derived from the male, in others from the 

 female. 



In the discussion on self-fertilisation the author mentions that in contrast 

 with the results of Castle and Morgan in Ciona intestinalis, he found 

 no self-sterility in experiments made with that species at Naples, and suggests 

 that the American form may differ from the Mediterranean in that respect. 



Doncaster (Cambridge). 



1180) Schulze, P., Über Trichius fasciatus L. 



(Berl. entom. Zeitschr. 55,1/2. p. 1-8. 1910/11.) 

 Bei dem Käfer Trichius fasciatus besteht ein — wenn auch nicht sehr 

 stark ausgeprägter — Geschlechtsdimorphismus. Die $$ sind abgesehen von 



