462 F. A. POTTS. 



well the sexual inactivity of the males. Tlie chief point of 

 interest lies in tlie constitution of the offspring of these six 

 individuals. Tlie young produced numbered 274, and of these 

 147 were hermaphrodites and 127 males. So numerical 

 equality of the sexes is secured in this species by cross- 

 fertilisation, a i-esult in striking contrast to that obtained when 

 R. m a rio u is was the subject of investigation. No permanent 

 effect was produced on the heredity of sex, for when 38 of the 

 hermaphrodites obtained by fertilisation by males were em- 

 ployed as parents for tlie next generation, 2964 individuals 

 were produced, of which only 7 were males, but the rest 

 hermaphrodites. 



Further evidence of the psychical decadence of the males 

 was secured in other species. Though nearly 100 males were 

 employed belonging to five species only a single successful 

 case of re-fecundation was observed, and in this (Rhabditis 

 duthiersi) the fertilised eggs gave 70 hermaphrodites and 

 1 male. 



The HERMAt'HRODiTES IN Hekmafhrodite Species. 



(1) The Hermaphrodite Glands in Rhabditis and 



Diplogaster. 



In Rhabditis sechellensis the structure and develop- 

 ment of the reproductive glands exactly correspond to the 

 desci'iption which Manpas gives of R, elegans and R. 

 dolichura. Though no new details can be given, it will be 

 convenient to summarise the changes which the hermaphrodite 

 gland goes through before oviposition commences in any of 

 the above three species. The three diagi-ams which illustrate 

 the description are partly after my own drawings for R . 

 sechellensis, but closely follow Maupas' sketches of R. 

 dolichura in Plate XXI, figs. 7a, 7b, and c. 



The hermaphrodite organ is double, its two divisions being 

 of equal development, and joining at the short and indefinite 

 common vagina. Each division is U-shaped, and consists of 

 a uterus, which extends from the vagina to within a short 



