1887.] 



ON CYCLESTHEKIA HISLOPI. 



57 



their activity. Thus I have founcl tliat whenever the temperature 

 in my aquary could be increased to any very high degree, e. g. 

 by exposing the latter to the direct rays of the sim, the speci- 

 mens were much more active than in the case of the tempera- 

 ture being lowered below the normal, when the animals were 

 often found resting in the very same place for days together, 

 generally concealed within some duster of Confervæ. 



On the 9th July I observed the escape of the brood from 

 one of the specimens, and in the course of the succeeding days 

 numerous young individuals were found in the aquary, together 

 with the adult. These rapidly increased in size, and after 

 some days became loaden with eggs, which developed in the same 

 manner to young. Thus, in the latter part of August the aquary 

 swarmed with numerous specimens of different size, representing 

 several successive generations. But no trace of any male speci- 

 mens could as yet be detected. On the 25th August, however r 

 when examining an adult female specimen, I found the compara- 

 tively full-developed young contained in its incubatory cavity to 

 be evidently of the male sex, the first pair of legs in all being 

 modified to well-defined grasping organs, or hands (see Pl. VIII r 

 fig. 1). At this time I had unfortunately to leave Christiania 

 for a while, and was thus prevented from watching the further 

 development of the male specimens. On my return, in the begin- 

 ning of September, I found but very few specimens still alive 

 in the aquary, and these surviving individuals seemed to be in 

 a rather morbid condition, their whole body, both the shell and 

 the limbs, being densely infested with parasitic thread-like growth, 

 encumbering to a great extent the motion of the animals, be- 

 sides impeding, it would seem, the free play of the branchial 

 feet. Although I carefully examined all the living individuals 

 still remaining, and likewise the numerous dead ones found at 

 the bottom, I failed in detecting either any male specimen or 

 any female specimen with „winter-eggs". In the few specimens, 

 still alive in the aquary, the incubatory cavity was either quite 

 empty or contained few, generally but one or two, developing 

 young. Among the empty shells found in great number on the 



