146 



free, rotating, and nibbling actively, while the hind parts remained 

 in the egg-shell ; and drawing back from time to time, as if loath to 

 leave its protection. Upwards of an hour elapsed before it was clear 

 from the shell. 



I have proved, by actual experiment, of many species, of widely dif- 

 ferent genera, and have reason to believe of many more, perhaps all, 

 that animals of the class Eotifera are not hermaphrodite, but bisex- 

 ual, the sexes being very distinct from each other in size, form, and 

 structure. Now in every case that I have examined, the male and 

 female eggs differ greatly in appearance, the latter alone displaying 

 the manducatory apparatus in the foetus. The smooth egg I proved 

 to be female ; it is possible that the prickly one may be male ; not, 

 however, necessarily because it is prickly, for in other genera I have 

 known prickly eggs to produce females. The subject, therefore, and 

 it is an interesting one, lies open for further investigation. 



In freedom, the manners of this Notommata are lively and energe- 

 tic : it swims wildly about, often in a zigzag course, turning first to 

 one side, then to the other, as it dashes rapidly along. Sometimes 

 it rotates on its long axis as it goes ; and at others it becomes sta- 

 tionary, adhering by the blunt extremity of its body, upon which it 

 turns as on a pivot. It is perpetually contracting and elongating, 

 and throwing its body into angular folds and contortions. 



EXPLANATION OF PLATE XX. 



a. Part of the sphere of a Volvox globator. 



b. One of its embryo clusters. 



c. d, e. Notommata parasita, within the sphere. 

 /, t. The gizzard of the Notommata. 



g. A smooth egg displaying the embryo. 

 h. A prickly egg. 

 The whole greatly magnified, but in different degrees. 



