This section is from the book "General Outline Of The Organization Of The Animal Kingdom, And Manual Of Comparative Anatomy", by Thomas Rymer Jones. Also available from Amazon: A General Outline of the Animal Kingdom and Manual of Comparative Anatomy.
(1159). This male is about 3/5ths 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 opening, 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 female, and the bands which bring the penis forward, clearly show it to be an extrusory organ, and to form a complete male apparatus. The sperm-bag evidently contains active spermatozoa.
* Vide Phil. Trans, for 1849, pis. 33 & 34.
(1160). Although Mr. Dalrymple never had an opportunity of observing any action beyond the extrusion of the penis, Mr. Brightwell, of Norwich*, has observed in seven different instances the direct copulation of the two sexes - clearly demonstrating this important fact, and thus establishing the dioecious character of this remarkable family.
(1161). But there is another circumstance connected with these Rotifers, almost without parallel in the animal creation. The male, as has been said, possesses the same general figure as the female; it has also the contractile cloacal cavity, named by Mr. Dalrymple "the respiratory sac," as well as the "water-system," furnished with the vibratory or ciliated tags. It has also the ordinary rotiferous apparatus at the head, through the agency of which its various movements of locomotion are performed; the red "eye-spot" likewise is distinct. It has, however, no mandibles, no pharynx, oesophagus, pancreatic glands, or stomach; there appear to be no organs of deglutition, digestion, or assimilation; only, at the lower part of the animal, on the other side of and opposite to the valvular opening, are three small oval bodies massed together, having no communication by tube or otherwise, but fixed in their places by short ligaments that may be rudiments of a stomach.
(1162). The difference of sex in these two forms, proceeding from the eggs of the same individual, is plainly evidenced by the fact, not only of the difference of structure, and the presence of active spermatozoa in the male, but by the observed fact of the intromission of the male organ into the vaginal canal of the female. That the male animal is produced by the female, and developed within the ovisac in the same manner as the female embryo, is also proved by many observations. The absence of all organs for the sustentation of life by food leads to the belief that it is created for a single purpose, and that its term of existence is very short. In this respect it somewhat resembles the drone, or male bee, whose utility seems to be confined to the impregnation of the perfect female or queen.
(1163). That a single impregnation is sufficient for the production of many young is proved by the female continuing to breed in water in which no male can be discovered; but young females so produced will not go on to develope others unless a male be born amongst them.
* Vide Ann. of Nat. Hist, for Sept. 1848.