94 



CRUSTACEA CIRRIPEDIA 



very much in the state characteristic of the Cypris larvae of other 

 Cirripedes, being furnished with two terminal hooks by which 

 attachment is effected. The thoracic appendages, of which there 

 are the normal number six, are reduced flabellate structures, and 

 the abdomen forms an indefinitely segmented lobe of consider- 

 able size. 



The animal appears to be in an arrested state of development, 

 and so retains some of the characteristics of the Cypris larvae, but 

 it is very doubtful how far these characters can be considered 

 primitive. 



Other forms are Dendrogaster astericola on Echinoderms, 

 and Synagoga mira on the " Black Coral," Parantipathes larix, at 

 Naples. 



Sub-Order 5. Apoda. 



Darwin described a small hermaphrodite parasite in the mantle 



chamber of Alepas cor- 

 nuta from Saint Vin- 

 cent, West Indies, 

 which lie named Pro- 

 teolepas birincfu. 



The body (Fig. 

 65) is distinctly seg- 

 mented into eleven 

 somites, the last three 

 of which are supposed 

 to belong to the ab- 



A--4I X^^^a*te^Lii-^^S^^i^ domen; there are no 



appendages except the 

 antennae by which 

 fixation is effected. 



FIG. 65. Proteolepas bivincta, x 26. A, Antennae; 

 a, b, 1st and 2nd abdominal segments ; O. ovary ; 



P, penis; T, telson ; 1-8, thoracic segments. (After The mouth-parts are of 

 Darwin.) 



normal constitution. 



This animal has not been found again since Darwin's dis- 

 covery, but Hansen 1 describes a number o peculiar Nauplins 

 larvae taken in the plankton of various regions, which he 

 argues probably belong to members of this group. A wide field 

 of work is offered in attempting to find the adults into which 

 various larvae grow. 



1 Plankton Expedition, ii. G. d. 1899. 



