W. Lilljeborg on the Genera Lii'iope and Peltogaster. 57 



Small specimens exhibit a good deal of vivacity, which decreases 

 with their growth. When v6ry small, the animals curve their 

 bodies in different directions, and exhibit vermicular movements, 

 constantly contracting the body from behind forwards. The 

 short tube surrounding the pallial orifice extends and becomes 

 slightly dilated, and from time to time one of the internal mem- 

 branes is pushed out, in the form of a sac, through this orifice. 

 Sometimes they retract the little tube, and then the orifice appeal's 

 as a depression. 



These small individuals differ greatly in form from those which 

 have completed their development. Of the smallest (figs. 3, 4) 

 the author once found eight individuals on the abdomen of a 

 small specimen of Pagurus cuanensis. The one figured (fig. 4), 

 which is distorted by its removal from the Fagurus, has at its 

 anterior extremity ih) the carapace of a Cirripede-larva in the 

 last stage of development (c), fixed in the depression of the re- 

 tracted tube of the pallium. It is a cast skin (fig. 5), and its 

 form is precisely that of the ordinary Jarvse of the Cirripedes in 

 what Darwin calls the " pupal stage." This larva has six pairs 

 of feet and a caudal appendage. The prehensile antennae are 

 large, and are fixed in the pallial orifice of the Peltogaster. As 

 a similar carapace was attached to three of the eight specimens 

 above referred to, and it has never been met with except on the 

 smallest and least developed Peltogasters, it appears certain that 

 it belongs to the last stage of development of the larva of Pelto- 

 gaster, and that it has remained fixed for some time after the 

 Peltogaster has issued from it. 



The small Peltogasters differ from the fully-developed indivi- 

 duals, especially in the structure of the organ of adhesion and 

 of the part of the body in the vicinity of that organ, — the dif- 

 ferences indicating that, as might be expected, these parts con- 

 stitute more powerful organs of suction than in the adult indi- 

 viduals. On comparing the figures (PI. III. figs. 3 & 4 with 

 1 & 2), the tube {a) by which the animal is attached to the 

 Pagurus differs greatly both in size and structure. This tube, 

 in the young animal, is much larger and of a more tender con- 

 sistence, except at the lower margin, which was attached to the 

 Pagurus. Within this tube there is another with thick cellular 

 walls, formed by the muscular membrane of the pallium, and 

 apparently also by the tube which issues from the ovarian sac 

 and unites with the preceding one. The margins of both, but 

 especially of the former, are bent outwards. Under the micro- 

 scope the end of the interior tube is seen to be principally com- 

 posed of cells and an intercellular substance. It presents two 

 concentric layers, — the outer belonging probably to the mem- 

 brane of the pallium, the inner to the ovarian sac. The cells of 



