84 THE SCOTTISH NATURALIST 



Cancer pagiiri/s, L. Bell's description of the hand of this form 

 "as rounded, without any ridge" applies only to the adult, for in 

 the young there are five or six distinct longitudinal rows of promi- 

 nent tubercles on the inferior surface. The parasites found in the 

 stomach are probably derived from its food, fragments of fishes 

 forming the usual bait in the crab-pots; the same Trematode,^ 

 however, is found in the tissues of both C. mxnas and this form, 

 where it occurs on the fibrous bands of the hepato-pancreas, or on 

 the ducts. Indeed in the stomachs are the lenses of fishes, ragged 

 portions of muscles and tendons, as well as crystalline styles 

 probably of mussels. In a fresh example a large number of small 

 air-bubbles formed on the surface of the stomach, and they kept 

 forming after the manner of those due to the application of acid 

 to a calcareous substance. The great lateral projection of the cara- 

 pace containing the so-called "liver" distinguishes this species from 

 Caninus mxnas, in which little of the soft tissues intervene between 

 the branchiae and the wall of the carapace. Their vitality in com- 

 parison with that of C. rnxnas is low. 



Carcinus mxnas, L. In some the large number of Trematodes 

 in the liver (hepato-pancreas) is remarkable, and they occur also 

 along the nerves, in the muscles of the wall of the stomach, on 

 those near the heart, on the male generative organs and other parts, 

 and they are found in small crabs only an inch across the carapace, 

 as well as in the older forms.- The Ascarides, however, are more 

 rarely met with. The vitality of the shore-crab is remarkable, many 

 surviving for six weeks in a damp cellar or in a botanic vasculum. 

 Bell states that it "simulates death as completely as do many 

 Coleopterous insects," and that he has seen them running about 

 in the soft state. Neither feature has hitherto been observed at 

 St Andrews, where thousands have been under notice. It seems 

 to moult at St Andrews chiefly in early autumn. Ova occur on the 

 pleopods in October as well as in December and January, so that 

 Bell's comment "as early as April and as late as September" 

 requires addition. The ectoparasitism of the common mussel 

 causes grave results, those settling in the sockets of the eyes 

 producing blindness, those in the gill-chambers fixing the branchial 

 "whips" with the byssus, and compressing the gills by their bulk, 

 whilst those in the abdominal region fix the pleopods and the 

 entire structure to the cephalo-thorax. 



In a small female, 2\ inches across the carapace, and which 

 showed commencing putrefaction, large brownish masses stretched 



^ Micros. Jotir.^ July 1865, Plate viii. 



- Vide Dr Wm. Nicoll's recent account of their structure. 



