290 Illinois State Laboratory of Natural Hiatoiy. 



stones and in the sand being, as a general rule, mucb 

 smaller than those in the seaweed. 



The living animals are sufficiently transparent to en- 

 able one to determine many facts concerning their struc- 

 ture, and such observations have been supplemented by 

 dissections and by the study of both longitudinal and 

 transverse serial sections, which show the general anat- 

 omy to be that characteristic of the Enchytrceidie. 

 The length of the larger specimens is a.pproximately 25 

 mm. and the diameter .5 mm. to 1 mm. The average 

 number of somites in several specimens taken at random 

 is 59, the minimum and maximum numbers noticed be- 

 ing respectively 53 and 69. The setae are somewhat 

 hooked at the proximal end, but are otherwise straight 

 or sometimes slightly curved. The most frequent num- 

 ber of setae in a bundle is three. There are often four 

 present in the bundles of the anterior region, and some- 

 times even six, but in the latter case they are in two 

 sets of three each, as though a second set had been 

 formed before the first one had been lost. In the bundles 

 of the posterior region there are frequently but two 

 setae present. The clitellum is on XII and XIII. I 

 found no dorsal pores. 



The length of the brain is one and a half to one and 

 three-fourths times its width, the ratio varying with the 

 state of contraction. Its sides are nearly parallel, the 

 anterior margin being slightly concave, and the posteri- 

 or slightly convex or straight. A careful examination 

 of this organ in several living specimens vshows that the 

 posterior margin is not concave, and that its convex 

 or straight appearance is not due to the peritoneal cells, 

 as suggested by Michaelsen (7, p. 36) in the case of E. 

 vejdovskyi. Two long tubular unbranched salivary 

 glands open into the alimentary tract upon its dorsal 

 surface, behind the pharynx, and extend into IV, having 

 a somewhat contorted course. Three pairs of septal 

 glands occur in IV— VI, but those of V and VI are one- 



