286 CH.ETODERMA. 



worms which creep about in mud do. Its intestine is usually almost 

 empty, its contents always consist of minute animal or plant organ- 

 isms, principally of diatoms, sometimes also of foraminifera or other 

 protozoans. 



" When the animal remains undisturbed in its burrow, the upper 

 mouth of the burrovv, as has been mentioned above, is entirely filled 

 up. Since Chcetoderma lacks the abdominal groove present in all 

 other Solenogastres, naturally none of the surface water finds its 

 way to the mouth opening. Accordingly the animal cannot, as for 

 example, is the case with the Siplioniata living in mud, feed upon 

 organisms swimming about in the sea water, but must be limited 

 exclusively to those found in the slime bottom. These are obtained,^ 

 naturally, by means of the anterior end. Not only the strong and 

 manifold movements of the prothorax, but also the occurrence of a 

 peculiar sense organ, the mouth shield, has this function. This 

 organ, for discussion of which we will have greater opportunity 

 later, is not only an organ for digging and grubbing, but is cer- 

 tainly a sense organ also. It is not present in other known Soleno- 

 gastres." 



Synopsis of species. 



a. Length of the body often exceeding 100 times the breadth (of 

 the narrowest part). Mouth-shield convex. Dorsal sense-organ 

 not covered by large spicules, surrounded on each side by a 

 tract covered with numerous small spicules. Tongue posteriorly 

 circularly closed, with large, lens-shaped thickenings of the cuti- 

 cle at the sides. Each gill with three free lamellae 



C. productvm. 



a'. Length of the body usually only 40-50 times the breadth 

 Mouth-shield flat. Dorsal sense-organ surrounded by a few 

 rows of small spicules, and almost entirely covered with large 

 spicules. Tongue open behind, no lens-shaped cuticular thick- 

 enings at the sides of the tongue. No free lamellse on the gills 



C. )iitUluIu7n. 



a". Shorter and thicker. Spicules flat and elliptical anteriorly, 



further back becoming broad keeled spear-like points, and 



toward the posterior end long stout prickles C. militare. 



C. PRODUCTUM Wiren. PI. 41, figs. 16-26. 



Length of largest specimens 130-140 mill., breadth of the pro- 

 thorax 2, of the metathorax 1-*, of the abdomen 3-2 mill. Much 



