18 G. O. Sårs. 



some other points. The figures given on the accompanying 

 plate will, I hope, render the present species easily recog- 

 nizable, and at the same time ellucidate the generic characters, 

 which have not been sufficiently pointed out by earlier authors. 



Biological Observations. — This form deve- 

 loped very abundantly in some of my aquaria, and was 

 watched for a considerable length of time. All the speci- 

 mens were of the female sex, multiplying in the usual par- 

 thenogenetic manner. Their fertility was exceedingly great, 

 numerous eggs and young ones being several times produced 

 by the same individuals. At the close of the season, how- 

 ever, the fertility considerably diminished, and the individuals 

 successively disappeared, without apparently having given 

 rise to any resting eggs. Nor did I succeed in detecting 

 even a single male specimen. 



In habits, this form conspicuously differs both from 

 the species of Moina and those of Simocephalus. More 

 generally the specimens were found near the bottom of 

 the aquarium, often congregated there in large shoals; but 

 sometimes one or other individual was to be seen swimming 

 up to the surface, or attaching itself by the back to the walls 

 of the aquarium, like the species of Simocephalus. The 

 swimming movements of the animal are rather slow, and 

 are effected in a somewhat jumping manner; but sometimes 

 these jumps are so very slight as to give the motion more 

 the character of a somewhat uneven run through the water. 

 In motion, the animal generally keeps its body in a some- 

 what prone attitude. I have never seen it swimming on its 

 back, like the species of Simocephalus, nor making such abrupt 

 and vigorous bounds as the species of Moina. 



The ova and embryos contained in the matrix are remark- 

 able for their great pellucidity and the absence of the usual 



