322 Miscellaneous. 



The parasite is lodged in the general cavity beneath the digestive 

 tube and partly concealed by the liver ; it is often folded back upon 

 itself in the form of a U, with the convexity turned towards the 

 posterior margin of the carapace. Sometimes we find two or three 

 parasites in the same crab. In an edible crab 1 inch broad I found 

 eight Fccampice ; several were concealed in the liver, others had 

 even penetrated into the muscles of the legs. In Pagurus the para- 

 site takes up its abode in the abdomen in the midst of the liver, 

 and it is sometimes visible from without through the skin. 



When extracted from its host and in an extended state the 

 Fecampia may attain a length of |- to I- inch. It is a worm with 

 a cylindrical body, attenuated towards the anterior extremity, 

 which is of a fine crimson colour, contrasting strongly with the 

 general colour of the body, snowy white with a faint rosy tint. 

 Two narrow, transparent, lateral lines start from the posterior 

 extremity and ascend to about one third of the length of the body. 

 These lines correspond to the ovarian glands. 



The integument is formed by an exoderm of flat, polygonal, 

 vibratile cells, without baciUi, among which open numerous very 

 voluminous cutaneous glands, the function of which will be stated 

 further on. The musculature is formed by annular and longitu- 

 dinal fibres. These muscles give the body peristaltic movements 

 resembling those of the Nemertians ; the muscular layer is, how- 

 ever, very weak, and on the least pressure the contents of the 

 animal flow with the greatest facility. 



The buccal aperture is anterior ; it leads into a not very distinct 

 pharynx, which is followed by a rudimentary digestive tube. 



The nervous system consists of two supraoesophageal ganglia, 

 united by a commissure and giving origin on each side to two 

 lateral nerves of considerable size. 



The whole mass of the body is composed of the generative organs ; 

 the smallest rupture of the integument permits the escape of large 

 cylindrical or irregularly ovoid cells, filled with clear vesicles and 

 active corpuscles, which I regard as forming part of the testis. It 

 is to these elements that the snowy aspect of the parasite is due. 

 The ovary is formed by very distinct cellular elements, and is accom- 

 panied by a voluminous deutoplasmigene, the cells of which have a 

 rosy colour, duo to very regular granulations ; the genital aperture 

 is situated at the posterior extremity of the body. 



On arriving at sexual maturity the Fecampia quits its host and 

 proceeds to crawl freely over the stones in the small pools which 

 the sea leaves full of water when it retires, and in which corallines 

 and Cluvtomorpha aerea grow in abundance. The Fecampia does 

 not keep its back upwards, but usually crawls upon one side with 

 the head slightly raised, and describes spirals, like a caterpillar 

 which is spinning its cocoon. In fact, our parasite soon surrounds 

 itself with a thick coat of threads secreted by the cutaneous glands, 

 and producing a regular case, which in form resembles a Prince- 

 Rupert's drop. This cocoon is white, formed by a web, which is 

 rather loose externally, denser towards the body of the animal ; its 



