PROTEOLEPAS BIVINCTA. 593 



would be to make a transverse slit, and subsequently to serve 

 as a grapnel to keep the mouth closely adpressed to its prey : 

 the other teeth might act in keeping the wound open. 

 When the mouth was thus closely adpressed over a wound, 

 the great power of shortening the whole body which the ani- 

 mal possesses (the oesophagus being closed), would, by the 

 subsequent action of the elasticity of the outer membrane, 

 almost certainly create suction, and thus cause the nu- 

 tritious juices of the Alepas to flow into the body of the 

 parasite. Hence I have called the mouth suctorial. 



Body. — This, as already stated, consists of eleven seg- 

 ments, of which the three posterior (abdominal) smaller 

 segments can hardly be distinguished, without dissection, as 

 separate from each other. The body is mainly occupied by 

 a vast ovarian sack (e, e, fig. 7), filled by innumerable ova : 

 and the three posterior segments by small testes and their 

 vesiculae seminales (i) : but I shall return to the internal 

 anatomy. The outer membrane, lined by delicate corium, 

 is thin, transparent, elastic, and covered by groups of 

 excessively minute blunt little points. The segments can 

 be plainly distinguished by their outlines, especially on the 

 ventral surface ; but they are rendered unmistakably dis- 

 tinct by the attachment of the muscles ; they can also be 

 perceived when the external membrane is perfectly cleaned, 

 by yellowish lines. The muscular system is highly symme- 

 trical and simple : along all eleven segments, there is a 

 narrow, medial, ventral and dorsal clear space ; on both 

 sides of which space there is a band of longitudinal muscles, 

 which, though encroaching on the two sides, and rather 

 largely on the dorso-lateral sides, may be called the ventral 

 and dorsal muscles. These muscles are striae-less, which is 

 the case with the homologous posterior thoracic muscles in 

 some other cirripedes : on the dorsal surface (lower surface in 

 fig. 7) they are more spread out, and consist, on each side of 

 the medial line, of four ribbons : this seems to be the case on 

 the ventral side, but the ribbons are here much more confluent: 

 in the seventh and eighth segments, the ribbons become 

 broader; but in the ninth, tenth, and eleventh, or three 

 posterior segments, they become much narrower, and some 

 of the fasciae disappear, so that these muscles can hardly 



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