allied to the genus Notommata of Ehrenberg. 157 



puffing out and drawing in the sides of its body as if to give them 

 their utmost dilatation. 



June 20th, 5 p.m. — Placed a young female and a male in a 

 trough by themselves and watched them very frequently till 

 eleven at night, and though they came very near each other no 

 conjunction took place. 



June 21st, 8 a.m. — Found the female dead and the male alive. 

 Put three other females to this male, and in a few minutes saw 

 the male as soon as he approached one of the females attach 

 his sperm-tube to its side and remain so attached fifty seconds. 

 Soon afterwards he attached himself to another very young 

 female and remained so attached seventy seconds. Could discern 

 this latter connexion of the end of the sperm-tube with the side 

 of the female very distinctly. 



4 p.m. — Saw in the trough, by the aid of the microscope with 

 a one-inch achromatic object-glass, a conjunction of a male with 

 a female. On approaching the female the male attached himself 

 by the sperm-tube to her side, and remained so attached nearly 

 a minute. Saw this most clearly, but owing to the movement of 

 the animals in the water it is almost impossible to see more than 

 that there is a distinct adhesion. 



Most of the above observations were made with a single lens 

 only, of two inches focus, and the others with the microscope. 



The animals seldom live above two or three days in the water- 

 troughs, but in larger vessels they may be kept alive three or four 

 weeks if they are supplied with water having Gonia in it. 



The question, as to the fertilization of the ova, remains to be 

 solved. It seems probable that they remain some time before 

 the young are produced, and it may be, that being buried in the 

 mud they remain there during the winter, and that the young 

 are not hatched till the warm weather of the ensuing summer. 

 On the other hand it is possible that ova are only produced by 

 the unimpregnated females, and that these ova are not fertile. 

 Careful and long-continued observations are necessary to deter- 

 mine these points. 



It is well known that several species of insects, in their imago 

 or perfect state, take no food, though provided with the usual 

 organs for that purpose ; but the case of the male of this Rotifer, 

 destitute of instrumenta cibaria and all digestive organs, is, we 

 believe, without precedent. 



Probably other dioecious animals of the same class exist which 

 have not come under observation. The whole subject invites the 

 further attention of naturalists, and we are glad to know that, 

 with reference to the immediate subject of this paper, they may 

 expect from the able pen and pencil of Mr. John Dalrymple those 



