Reproduction.—It is not yet accurately de termined what are the organs of reproduction in these animals. That which was regarded by Cuvier as the ovary in the Lepads, is supposed by Professor Wagner and M. St. Ange to be the testicle; while Professor Burmeister has satisfied himself that it is the liver. The ex tent, structure, and relations of • the ovary are still doubtful. It is certain, however, that all the known Cirripeds are hermaphrodite.
The testicle, according to Professor Wagner and M. St. Ange, is a large granular organ (y, fig. 344), expanded over the sides of the Anatifa, the first pair of arms is thicker and stronger than the others ; the sixth pair is the longest. Dr. Grant says, " the arms are not only minutely jointed to their extreme points, but, also, the innumerable fine cilia which pro ject inwards from their surface are themselves minutely jointed, and by the aid of the micro scope, we can perceive that these jointed cilia are also ciliated on their margins." When the animal is at rest, with the valves of the shell closed, the arms are coiled up, and lie close to one another ; but, at ,other times, circumstances being favourable to the perform ance of the function of respiration, they are ex tended simultaneously so as to project from the shell,—radiate and plumose in their arrange ment. Many species extend and contract their arms with considerable rapidity, as often as forty or sixty times in a minute ; the smaller species m6re frequently than the larger.
Considering how extensive the surface is which is exposed in the arms between the two rows of cilia, and that a vessel seems to run immediately beneath the delicate covering of these organs in that situation, it appears proba ble that the arms are very efficient agents in the function of respiration.
Secretion.— We have failed to ascertain satis visceral mass, and around the digestive canal, from the stomach to the anus, passing even into the bases of the arms, immediately beneath the muscular tunics which cover the body on both sides. It is composed of numerous minute lobules, about thoth of an inch in diameter in the common Lepads, soft, white, grouped toge ther by branched ducts (q, q, fig. 344), which, after uniting into three or four principal trunks,* meet in a large central receptacle (r), some what analogous in relative function to the vas deferens of vertebrate animals. The seminal fluid passes from this central receptacle by a short and straight duct into a large canal (t, t), which may be compared to the seminal vesicle.
It pursues a tortuous course towards the base of the tubular process, -where (k) it is joined by its fellow of the other side, and enters the canal of the process which forms a kind of caudal prolongation of the abdomen (t', t'). This canal runs to the "distal extremity, and opens by a minute orifice fringed with very fine hairs. In Otion Cuvieri the two canals are continued distinct to the very point of the process, where there are two openings.* The walls of the organ, which we have compared to the seminal vesicle, have a glandular structure, which Cuvier imagined to be the testicle. The re searches of Professor Burmeister have led him to the same conclusion. IIe says it can be no thing but the testicle.t Cuvier, as well as Lamarck, regarded what we have called the testicle as the ovary, and believed that the ova were impregnated, in the course of their passage along the oviducts, by the seminal fluid flowing from the testicle investing these canals. The granular lobules of the true testicle, which were supposed to be immature ova, are found always in the same state, and what are more distinctly ova are found within the peduncle.t The lengthened tubular process 0', t',.fig. 344), through which the excretory duct of the testicle passes, is articulated ; the margin of each joint is fringed with minute hairs. In Otion and Coronula, Burmeister found large canals closed at both extremities, within the process, in addition to the ducts from the testi cle. This organ is generally found after death bent upwards on the abdoniinal surface ; but, during life, it is in continual motion. Its use is, probably, to carry the seminal fluid back wards beyond the current caused by the move ments of the arms, in the event of there being mutual impregnation between separate indivi duals ; or towards the mouths of certain ducts which communicate with the ovary within the peduncle in case of self-impregnation taking place. in this view it must be regarded as the penis ; and it is so called by the most recent authors on the subject—Wagner and Burmeister. Mr. Thompson calls it an ovipo sitor ; ,and conjectures that, after their expul sion from the ovary, (understanding by this what we regard as the testicle,) the eggs are conveyed by it into the cellular texture of the pedicle. How they pass from this depository into the general cavity, where they afterwards form two or three foliated groups, he confesses himself unable to explain.