446 ¥. A. POTTS. 



in a bath at 26-28° C. Under these conditions the ovary con- 

 tinued to ])roduce large-yolked eggs, and at first these wei-e 

 fertilised and laid, but after they had completed a few divi- 

 sions they became disorganised. With eggs which later 

 passed from the ovary into the utei'us fertilisation did not 

 apparently take effect. No egg-shell was formed, and the 

 uterus became full of an amorphous, yolky mass. 



It seems, then, that the limits of reproduction lie in Diplo- 

 gaster maupasi between 19° C. and 25° C, though life 

 may be continued at slightly higher temperatures. It w;is 

 found impossible, however, to keep cultures at a constant 

 temperature of over 30° C. 'J'lie individual worms became 

 rigid and after a short exposure died. It is seen that the 

 free-living nematodes are most sensitive to increased tempera- 

 ture in the egg stage, when they can hardly endure high 

 summer heat. The adult is also likely to succumb at 

 temperatures which must be common iii ti-opical countries 

 at least. The encysted larvae are probably the most resistant 

 stage, and it must be supposed that these animals depend 

 for their existence in periods of exceptional heat to their 

 capacities for survival in this condition. 



The Males op Hekmaphrodite Species, 



(1) Structure and Organisation. 



The male sex in Rhabditis and Diplogastei', as in all 

 nematodes, is sharply discriminated by the relation of the vas 

 deferens to the alimentary canal, and by the Avell-defiued 

 secondary sexual characters, including a membranous bursa 

 for adhesion to the female during copulation, and an arrange- 

 ment of spicules for insertion into the vulva to facilitate the 

 transference of the spermatozoa. 



The males of hermaphrodite species occurring in such 

 small numbers, and apparently taking no part in reproduction, 

 might naturally be expected to show some marked signs of 

 degeneracy in organs other than the reproductive system. 



