154 Mr. T. Brightwell on a dioecious Rotifer 



somewhat larger than either species, and is without any caudal 

 appendage whatever. It has also no anal opening, the faeces 

 being rejected by the mouth. 



The general arrangement of the internal anatomy is analogous 

 to that of N. Syrinx. The stomach is a pyriform sac or bag with 

 many cells, but without any lower opening. The two reniform 

 bodies above the stomach, supposed to be hepatic or pancreatic, 

 are very conspicuous in this species. Beneath the stomach and 

 lying transversely and of a horse-shoe form is placed the ova- 

 rium, which in the young is a cylindrical bipartite organ, the 

 parts being united by a central knob. On one side of the body 

 is a very delicate membranous bag, often plicated. This organ 

 is united to the ovisac, lying below, which ovisac receives the ova 

 or foetus, and is connected with a conspicuous opening in the side 

 of the animal from which the ova and young are expelled. On 

 the other side is placed the singular structure deemed by Ehren- 

 berg the fertilizing organ. This consists of two or more delicate 

 vermiform tubes running from the neck to the lower part of the 

 body and curled at each extremity, and of a minute muscle or 

 fibre running from the upper to the lower coil of the tubes inter- 

 nally, and upon which are arranged sometimes as many as twenty 

 little cylindrical bodies somewhat resembling Vorticella, and in 

 the interior of which may be discovered a strong spiral vibratile 

 motion varying in intensity *. 



At the bottom of the body of the female is generally seen a 

 foetus (see PI. VI. fig. 3), which is found in all states, from the 

 earliest period of gestation to a perfectly developed animal, and 

 in which, in its maturer state, may be detected, while still in the 

 body of the mother, the red eye, cilia actively playing, and most 

 of the other organs of the adult animal. The young, when ma- 

 ture, are expelled from the side of the parent by the opening 

 above mentioned, and are evolved by a violent parturition. They 

 are for some days considerably smaller than the parent animal. 

 The eye, the stomach, the two kidney-shaped bodies above it and 

 the double ovary beneath may be most clearly seen in the female 

 young. In other individuals, but more rarely, are seen one or 

 two large round ova. When two ova are present they are placed 

 one above the other, the lowest being always found opake and 

 striated, and the upper one more or less transparent and reticu- 

 lated, or covered with minute follicles. In these transparent 

 ova may be detected the germ, or more advanced state, of the 

 opake ova (see PI. VI. fig. 4). The opake ova are dropped by the 

 parent animal, but we have never seen any young in, or proceed- 

 ing from, the ova. 



* A quarter of an inch achromatic object-glass is necessary to see these 

 organs. 



