434 



CRUSTACEA ENTOMOSTRACA. 



Sub-order 5. ASCOTHORACICA. 



These are parasitic, hermaphrodite or dioecious Crustacea generally 

 living embedded in the tissues of their hosts. They are perhaps allied 

 to Cirripedes but present no very clear affinities with any of the other 

 sub -orders. A nauplius larva is found in Laura, and in Dendrogaster a 

 later larval stage is known which somewhat resembles the Cypris larva of 

 the Cirripedes. The antennae are, however, formed on a quite different 

 plan, and no peduncular attachment is found in any of the four genera. 



oy. 



FIG. 279. Laura gerardiae Lacaze-Duthiers. a, body partly removed from the sack; 6, a 

 papilla from the outer surface of the sack ; c, complete sack attached to the skeletal stem 

 of Gerardia (G), with the orifice towards the spectator, and in profile, ant. antennae ; /cau- 

 dal fork ; F hepatic diyerticulum contained between the layers of the mantle sack ; g.s. 

 supra-oesophageal ganglion ; i intestine; o $ (?) male orifice; o p female orifice; 

 opening of sack ; in a, shows the position of the opening ; ov ovary ; v vessels. 

 (From Gruvel, after Lacaze-Duthiers.) 



The single pair of antennae are short and pointed and the mouth parts 

 &re contained in an oral cone. Five or six pairs of appendages, simple or 

 biramous (absent in adult of Dendrogaster), succeed and a pointed abdomen 

 may be present, terminating in a caudal fork. Diverticula of the 

 alimentary canal and the ovaries lie between the layers of the mantle. 



Laura gerardiae Lacaze-Duthiers (Fig. 279) * lives enveloped, except 

 for a small orifice, by the polyps of the colonial antipatharian Gerardia, 

 L.-Duthiers (Savaglia Nardo). The enormously developed mantle, or sack, 

 contains between its folds the ovaries (ov) and diverticula of the ali- 

 mentary canal (F), and its surface is beset with prominences (6) embedded 



* H. de Lacaze-Duthiers, Histoire de la Laura gerardiae, Mem. de 

 VAcad. des Sciences, T. 42, Paris, 1882. 



