Publisher's Synopsis
Excerpt from The Voyage of H. M.S. Challenger: Zoology; Report on the Cirripedia Collected by H. M.S. Challenger During the Years 1873-76
The species of Lepas, the Cypris-larvae of which have served me for comparison, was the Lepas austmlis, Darwin. It is not only very characteristic on account of its great size, but it is also the best known Cypris-larva, as it served first for the investigations of Darwin, and again some years ago for the studies of Claus. The latter has given a very good figure of the internal structure of this larva as seen in a sagittal section. My figs. 1 and 2 on pi. II. Very closely correspond to that of Claus. My fig. 1 was drawn from a preparation made by dividing the body of the Cypris-larva of Lepas australis into two nearly equal halves by means of a sagittal section. The rounded spot (a M) is the adductor muscle of the two valves of the Cypris-larva the straight line at the under side of the valve represents the ventral side, the convex one the dorsal side; the extremity on the left of my figure the frontal (cephalic), the one facing it the hinder (abdominal) extremity of the body; from the way in which the spines of the legs are stretched out at the ventral side it is clear that there is a slit-like opening between the adductor muscle and the hinder extremity of the body. In fig. 2 of P]. I., representing a longitudinal section parallel to and at a little distance from the ventral margin, this orifice is also distinct. This is the only place where the interior of the sack or mantle (as Darwin calls it) is in open communication with the surrounding water.
The body of the future Lepas is enclosed within the sack and has also a wall of its own; on one side (the right hand side of the figure) this wall is very distinct, and it passes over near the middle of the dorsal margin into a transverse invagination which almost reaches up to the ventral side. It is by this invagination that the division of the body into a capitulum and a peduncle is brought about; what in fig. 1 of P1. II. Is placed on the right hand side of the invagination is the capitulum, what is placed on the left hand side the peduncle. As the invagination of the dorsal wall does not reach' as far as the ventral side, a direct communication remains between the capitulum and the peduncle. Through this commissure, which is very narrow in the full-grown animal, pass the oviducts and the nerves destined for the peduncle.
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