14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. "J 2 



is Still more developed and is produced into branched lobes. In 

 Laura the mantle is covered with stellate papillae penetrating the 

 tissues of the host and presumably absorptive. In all cases the mantle 

 contains ramifications of the enteric diverticula and portions of the 

 gonads. In Laura the body is divided into six " thoracic " and three 

 limbless " abdominal " somites, and ends in a caudal furca. In 

 Petrarca and in Dendrogaster the body is unsegmented. 



In these three genera a pair of preoral appendages is present and, 

 except in Laura, are armed with hooked spines suggesting that they 

 are organs of fixation. They are inserted, at least in Laura, at the 

 sides of the buccal region, and are more or less enveloped by the 

 mantle. 



The cement glands appear to be absent, and the mouth parts are 

 more or less reduced, but appear to be adapted for piercing. 



The thoracic appendages are biramous and articulated only in 

 Synagoga. In Laura they are uniramous and indistinctly segmented, 

 and the first pair are long and slender. In Petrarca they are still 

 further reduced, and in Dendrogaster they are represented only by 

 some indistinct papillae. 



In all three genera the gut ends blindly, and the hepatic diverticula, 

 which are large, extend into the mantle. The nervous system is 

 reduced. An eye is said to be present in Synagoga. In Laura the 

 oviducts open at the base of the first pair of cirri. 



The larva of Laura is a nauplius lacking the frontolateral horns; 

 in Dendrogaster the larva hatches as a peculiar cypris with only five 

 pairs of biramous thoracic limbs. 



In the Apoda the curious Proteolepas hivincta is elongated and 

 maggot-like, with no trace of a mantle nor of appendages other than 

 a pair of adhering antennules. The mouth parts, borne on the first 

 " segment," seem to be adapted for piercing and sucking. The ali- 

 mentary canal is greatly reduced ; according to Darwin only the 

 oesophagus is present, and there is no trace of stomach, rectum or 

 anus. 



THE CRINOIDS AND THE STARFISHES 



In the crinoids during their development the mouth moves from 

 the ventral surface onto the left side, indenting the left hydrocele 

 and the left posterior coelome, and continues its migration until it 

 comes to lie at the posterior end beside the anus. When it has 

 reached this point the hydrocoele ring closes. As a result of this 

 movement the right posterior coelome has also shifted and come to 



