GENERAL FEATURES, INIETHODS, ETC. 25 



carinala aiul Stylumcnia sulmtori, crawl about freely over the sea bottom, though 

 it is possible also that they have been loosened from some host. 



The relation of mollusc and coelenterate has not been thorouglily worked 

 out, but there are many indications and some definite i)roof that it is a genuine 

 case of parasitism and not an accidental association or a case of commensalism. 

 In Drepanomenia vantpijrdla from the Hawaiian Islands the proboscis of one 

 individual was inserted into the bod}' wall of some species of Epizoanthus, many 

 of whose reproductive and other cells had been withdrawn so that here there is 

 no doubt that this Solengastre is a parasite. The presence of nematocysts in 

 the alimentary canal of several other species, including most of the species of 

 Strophomenia, indicates that they likewise are in the same categorj'. " Hubrecht 

 ('(SO) states that a bit of alcyonarian coral was found in the mouth of P. sluitcri, 

 but he calls attention also to the fact that diatoms and entomostracans occurred 

 in the faeces in the cloacal cavity, and Heuscher ('92) records the presence of 

 Entoniostraca in the gut itself. It thus develops that the diet of such species 

 is varied, and it is possible that such forms as P. vagans and P. desiderata which 

 were found crawling about on plants belong to this same class. 



So far as known the food of the Chaetodermatidae consists of microscopic 

 organisms and organic remains which they scoop up while burrowing through 

 the ooze. " Wiren ('92) believes that the buccal j)late (Mimdschild) acts as a 

 digging organ, and this may indeed be the case Init the exceedingly small amounts 

 of inorganic material, which make their way into the digestive tract, indicate 

 that in addition to functioning in a purely mechanical fashion it manifests a 

 decided selective action. \Yhcn selected the food is carried backward by the 

 great conical tooth in the genus Chaetoderma, and in the form of a more or less 

 spherical bolus, mixed with the secretion of the salivary glands, is carried into 

 the mid gut. In Prochaetoderma and especially Limifossor the radula and its 

 supports are of large size and indicate active, predatory habits, but the contents 

 of the gut are essentially the same as in Chaetoderma. 



Color, Size. — In a preserved state the skin of the Solenogastres is usually 

 unpigmented, tlu^ light yellow or yellowish brown tint of the animal being due to 

 the cuticle investing the body. In many species, especially of the Chaetoder- 

 matidae, this may be obscured to a greater or less degree by the multitudes of 

 refringent sjiicules imbeddetl in it or by some of the internal organs. The liver 

 for example is often dark brown, and shining through the translucent body wall 

 and the overlying cuticle and spicules, gives a decided frosted gray tint to .several 

 species. The red color of the blootl plasma may impart a pinkish tinge espe- 



