ASPLANCHNIA. 447 



minute masses whereof the tube is formed are prepared. Into this 

 cup-like organ foreign particles are continually brought, at the will of 

 the animal, by ciliary action, and collected into little pellets, which are 

 deposited as quickly as they are completed in successive rows around 

 the foot, until a tube is formed of sufficient size for the lodgment of the 

 little Rotifer (fig. 231, 2, a, 6). 



(1158.) In the remarkable genus Asplanchnia, it has been ascertained 

 by Mr. Dalrymple* that these animals are bisexual, and, moreover, 

 that the male individual is one of the strangest organisms as yet disco- 

 vered. In the female the sexual apparatus is very completely developed, 

 consisting of an ovary, an ovisac, vaginal canal, and vulva, the whole 

 being so transparent that the development of the embryo throughout all 

 its stages is readily observable, and its progress traced from the time 

 of the formation of the egg to its birth. The eggs are of three kinds : 

 the first is of ordinary structure, wherein the formation of the female 

 embryo is easily witnessed while contained in the body of the parent ; 

 but towards the latter end of the season, ova are furnished of a totally 

 different character, which are apparently destined to remain through 

 the winter undeveloped until the following year. In a third description 

 of ovum an embryo may be observed to become developed gradually 

 from a germinal vesicle until it begins to assume a definite shape and 

 independent movement, when we are at once struck with the remarkable 

 peculiarities observable in its form, size, and organization ; and this is 

 the male, which will require special description. 



(1159.) This male is about -Jths of the size of the female, generally 

 resembling it in shape, but more flattened at the lower part, or fundus, 

 and more prolonged at the side, corresponding to the vaginal opening in 

 the female, which in the male presents a similar valvular opening, though 

 comparatively smaller in extent. Within this valve is observed a short 

 canal, leading to a large spherical bag, which may be distinctly seen to 

 be filled with molecular bodies in a constant tremulous movement. 

 From this sac, which Mr. Dalrymple denominates the " sperm-bag," a 

 short but thick rounded body projects into the canal before mentioned 

 as leading to the lateral opening ; and around the extremity of this 

 projecting process, and even within it to a short distance, is a visible 

 ciliary motion, indicating a canal ; on the neck of the sperm-bag is a 

 fasciculus of delicate muscular fibres, which are inserted along the 

 commencement of this evident penis, and over the latter organ the 

 membranous sheath is reflected. Muscular bands, arising from the 

 tegumentary parietes of the animal, in the vicinity of the valvular open- 

 ing, go to be inserted into the root of the penis, and may be frequently 

 observed drawing it up to the opening, and even extending it beyond 

 the body of the animal. Muscles also for the purpose of opening the 

 valve, very similar to those employed for the same purpose in the 

 * Vide Phil. Trans, for 1849, pis. 33 & 34. 



