404 D. J. SCOURFIELD ON THE SWIMMING OF DAPHNIA^ ETC. 



and Simocejyhalus — i.e. not quite parallel to the long axis of the 

 body, but slightly inclined towards the back ; while in respect 

 to the general effect of gravity, Ceriodaphnia will be found to 

 closely resemble Daphnia, whereas Scapholeberis will resemble 

 Simocephalus. 



Although in the present paper I have limited myself to the 

 swimming habits of Daphjiia and its allies, it must not be 

 supposed that it is only among these forms that striking differ- 

 ences exist. There is at least one other case among the 

 Entomostraca, and it is even more remarkable, for the differences 

 occur between the species of a single genus, namely, Cyclops. 

 Why such species as C. fuscus, C. albidus, C. serrulatus, C, 

 prasinus, etc., should always swim back downwards, whereas 

 C viridis, C. strenuus, C. bicuspidatus, C. vernalis, etc., always 

 swim back upwards, and why, again, C. leuckarti should always 

 swim vertically, is a subject which it has long been my desire 

 to fathom. Hitherto I have not been able to satisfactorily 

 account for these peculiarities, but I hope, when the method of 

 examining these creatures, as indicated above, has been further 

 developed, that we shall get some light on the matter. 



Journ. Quekeit Microscopical Club, Ser, 2, Vol. VII., No. 47, November 1900. 



