692 CIRRHOPODA. 



the shell ; which process is, at times, so much son has not seen the change actually going on, 

 elongated as to admit of the eggs hanging out but he has satisfied himself that what he re- 

 in groups from the brachial aperture, beyond gards as the free-moving embryo fixes itself by 

 the extremities of the arms. Burmeister has a spot on its dorsal aspect between the two 

 observed that, after the escape of the embryo, shells, which spot can be seen during its free 

 the shells remain connected with the parent, state. When fixed, the base of adherence ap- 

 forming a loose net-work. This author seems pears to be broad like that of an Actinia : from 

 to regard these groups of eggs within the man- this it rises in a conical form, truncated. The 

 tie, and the tissue in which they are imbedded, flat sides of this cone are coated with six shelly 

 as constituting the true ovary. In each of the plates, so arranged as to leave a large space in 

 individuals of Anatifa striata which came under the middle uncovered. This space is closed 

 his observation, he computed that there were by the old shells of the embryo state, which 

 about 4000 eggs in the ovary. Mr. Thompson are made to move up and down as the opercule 

 calls these groups of ova conceptacles ; and does in the adult animal, admitting of the 

 says that " each has a separate attachment at egress and ingress of the arms at the animal's 

 the sides of the animal to the septum, which pleasure. Through this shell two large black 

 divides the cavity occupied by the animal from spots like eyes can be distinguished. Mr. 

 that of the pedicle."* The retention of their Thompson found in the young of the Balanids, 

 ova, grouped in separate packets on the surface six pairs of arms, cleft ; each arm with' two ar- 

 of their bodies, after their expulsion from the ticulations. The first casting of the shell, after 

 ovary, constitutes another point of resemblance the animal has fixed itself, is followed by an 

 between the Cirripeds and Crustaceous animals, increase in the number of articulations in each 



With regard to the anterior canal within the arm ; and this number is further added to at 



ovary, little has yet been determined. We every succeeding shell-casting. Even the old 



have particularly examined it in Otion, and full-grown animals, according to Mr. Thomp- 



find that, like its fellow of the dorsal aspect, it son, cast their shells. 



leaves the ovary at its inferior edge, whence it Very recently Mr. Thompson has made a 



opens into a small cavity situated between the still more satisfactory series of observations on 



intervalvular ligament and the lining membrane the development of some of the Lepads, of the 



of the visceral cavity. We have not succeeded genera Cineras, Otion, and Lepas. These he 



in discovering any orifice in the walls of this obtained from the bottoms of vessels in the 



cavity, although, from the results of some of harbour of Cork. They hatched eggs in large 



our experiments we think it probable that there numbers, and afforded him the means of ascer- 



exists a small one just above the brachial slit, taining, entirely to his own satisfaction, that, at 



If so, is it not likely that this is the passage in- its first exclusion from the egg, the Lepad, like 



tended for conveying the fecundating liquor the Balanid, is a natatory crab. He found a 



from the orifice of the tubular process connected considerable difference between the larvae of 



with the male organs to the ovary ? When the the two classes. The newly-discovered one of 



body is exserted through the brachial slit, the the Lepads he describes as " a tailed monocu- 



point of the process can easily be brought into lus, with three pairs of members, the most an- 



contact with the outer surface of the cavity terior of which are simple, the others bifid, 



above described. having its back covered by an ample shield, 



The development of the egg and the young terminating anteriorly in two extended horns, 



of the Cirripeds has recently become an object and posteriorly in a simple elongated spinous 



of interesting inquiry in consequence of the process." 



novel results announced by Mr. J. V. Thomp- The general appearance of this larva is not 



son in his " Zoological Researches," (1830, unlike that of the Argulus armiger of La- 



4th Memoir.) This gentleman has published treille.* 



an account of observations made on what he Very recently Messrs. Audouin,f Wagner,} 

 believed to be the young of Balanids, from and Burmeister, have corroborated the state- 

 which he concludes that, on their first exclusion ments and supported the views of Mr. Thomp- 

 from the egg, they closely resemble some of son. Professor Burmeister has detailed the 

 the branchiopodous Crustacea, that they pos- results of his observations with great minute- 

 sess the power of free locomotion through the ness. It appears that they were made chiefly 

 water by means of setiferous arms projecting on individuals of Anatifa striata, procured in 

 from within a bivalve shell, and that they the North Atlantic Ocean, and preserved in 

 have very obvious pedunculated eyes. Minute spirits ; partly also on Lepas anserifera. (Linn.) 

 animals, bearing these characters, and having The results of these observations have led Pro- 

 some resemblance to species of the genus fessor B. to divide the development of the Cir- 

 Cypris, were placed by Mr. Thompson in a ripeds into five stages or periods. Thejirst of 

 glassful of sea-water. Soon after, on looking these is the state of egg ; the second is that of 

 for them, he could not find them in the water, 



but he found in their room several very young * Phil Trans< 1835j pt> iL 355t <, Discovery of 

 balanids, which, from the appearance they pre- the Metamorphosis in the second type of the Cirri- 

 sen ted, he concluded to be really the same peds," &c. 

 animals that he had originally placed in the t Ann des Sc. Nat. n. s. iii. j 

 water, changed by n.etamorphosVMr.Thomp- ^jSStftJftt&t '& im? "" 



$ Bcitrage zur Naturgcsch. der Rankenfusser. 



* Phil. Trans. 1835, 356. Berlin, 1834. 



