THE CIRRI FED I A 



119 



mouth-parts are normal, and the cirri are all present, but are composed 

 of a restricted number of segments. The alimentary canal is com- 

 plete, and in some cases even vestiges of the ovaries have been 

 found. In a second group, comprising S. vulgare, S. gigas, etc., the 

 peduncle and capitulum are no 

 longer distinct, and the capitular 

 plates are vestigial (Fig. 69, B). 

 The mantle - cavity is greatly 

 reduced, and the cirri are re- 

 presented by six pairs of unseg- 

 mented processes each carrying 

 two or three long setae. The 

 gut ends blindly. In a third 

 group of species, represented by 

 S. stromii, S. velutinum, etc., the 

 capitular plates have entirely 

 disappeared and the structure is 

 still further degenerate (Fig. 69, 

 C). It is among the species of 

 the third group that complete 

 separation of the sexes occurs, 

 the large individuals being quite 

 devoid of male organs. 



The degree of degeneration 

 exhibited by the males appears 

 to be correlated, to some extent, 

 with their place of attachment to 

 the female or hermaphrodite in- 

 dividuals. The less - modified 

 males are lodged in fossettes in 

 the margin of the mantle, while 

 in those species where the modi- 

 fication is more profound the 

 males are attached within the 

 man tie -cavity below or behind 

 the adductor muscle. 



.,,,. ._ A, dwarf male of Ilia r/vorfritnitrf*. Cc, 



In Una the male (r Ig. / 0) IS duct of cement-gland ; C.E, terminal part of 



modified in a manner somewhat 

 different from that observed in 



The peduncle is long seminal vesicle ; c, cirrus of last pair. B, 



, . , , , posterior end of body with caudal furca. 



and the mantle is greatly reduced (From Gruveis Monographic.) 



and does not enclose the body. 



The mouth-parts are normal, but there are only two pairs of uni- 



rainous cirri. The alimentary canal is complete. The penis is 



short, in correlation probably with the length and flexibility of the 



peduncle and also with the place of attachment of tfie males, 



