48 W. Lilljeborg on the Genera Liriopc and Peltogaster. 



was transversely oval ; at the posterior part the anal aperture 

 was seen in a small depression, and surrounded with dark points 

 and a slightly projecting border. The body was less convex be- 

 low than above, and had no longitudinal fissure. The colour 

 was yellowish white. 



Sacculina Carcini, J. V. Thompson. 



Ent. Mag. vol. iii. p. 452 (1836). 



Pachybdella Carcini, Diesing. 



The author observes that the form of this animal changes 

 remarkably according as it contracts the pallium more or less, or 

 absorbs a larger or smaller quantity of water. When immersed 

 in spirits, still fixed to the Crab, the latter, by strongly drawing 

 up the abdomen, causes the Sacculina to acquire a flattened 

 form. By absorbing water it becomes more inflated and rounded. 

 After emptying and abandoning the oviferous tubes, the animal 

 acquires a more contracted form. 



The author cites Thompson's descriptions of the larva of 

 Sacculina, and copies his figures, which he considers to confirm 

 the opinion, put forward in the preceding memoir, that Sacculina 

 is a Cirripede ; he also points out the error made in the report 

 of Thompson's paper in Wiegmann's 'Archiv' for 1837, and 

 already indicated by us in a note on Leuckart's Memoir on 

 Sacculina^, according to which Thompson regarded this parasite 

 as " belonging to LernEeadse," whilst in reality his remarks evi- 

 dently tend to show that he considered its nearest affinities to be 

 with the Cirripedia. 



The living Sacculina (PI. II. fig. 1, nat. size) shows scarcely 

 any movement, except that it from time to time contracts the 

 aperture at b, so that the wrinkles of the pallium round this 

 aperture become more numerous, and form a depression as 

 shown in the figure. The pallium is slightly transparent, so 

 that the oviferous tubes may be indistinctly seen. The pallium 

 consists of three distinct membranes. Externally there is a 

 tolerably thick and opake yellowish-white chitinous membrane, 

 having on its inner face a pretty thick cellular layer. In this 

 cellular layer branching and anastomosing tubes containing a 

 darker matter are observed : these the author thinks may be 

 muscular tubes. A thick and opake membraue, slightly attached 

 by connective tissue, lies beneath this layer, and appears to pre- 

 sent a more complicated structure. Externally there is a thin 

 chitinous lamella, on which there are a great number of bands 

 of a more solid structure, rising a little above the lamella, and 

 becoming confounded with it at the extremities and sometimes 



* See Annals, ser. 3. vol. iv. p. 424. 



