160 



EXTERNAL CHARACTERS 



The body is slender and has a length of 13-17 mm. In transverse 

 section it is circular and has in the region of the clitellum a maximum 

 diameter of 0.34-0.43 mm. In living specimens the body appears 

 opaque and whitish. The prostomium is blunt, rounded, and rather 

 short. The intersegmental grooves, excepting the first three or four, 

 are very obscure. The number of somites is variable, the extremes 

 being 44 and 60. The clitellum is well developed and occupies XII- 

 XIIL The setae bundles usually contain 4-6 setae. Sometimes the 

 number is as high as 8, but this happens rarely. In the last four or 

 five somites the number varies from 1-4. The setae are simple and 

 straight except for the distinct bend at the proximal end. They are 

 of different lengths in a bundle, the outer ones being longest and 

 stoutest. The head pore is small and on o/I. In one of the prepara- 

 tions the lymphocytes, which are abundant in the anterior part of the 

 body, were passing out through this opening at the time of fixation. 

 This seems corroborative of the statement of Cnenot ('97, p. 90) that 

 the coelomic fluids are often exuded through the "dorsal pores" when 

 the animal comes in contact with some irritating substance, and it 

 is possible that in this instance the chloretone was the irritating sub- 

 stance. 



The cuticula is thick, firm, and approximately uniform in thick- 

 ness throughout the length of the body. In the first few somites the 

 hypodermis is about 2-2>^ times thicker than the cuticula, but through-" 

 out the greater part of the body the latter has about the same thick- 

 ness as the former, being sometimes even slightly thicker. The pres- 

 ence of the thick cuticula in these specimens evidently supports the 

 statement of Vejdovsky ('79, p. 11) that species living in compara- 

 tively dry localities are characterized by a thick cuticula. The speci- 

 mens of oconeensis were found under the decaying bark of fallen tim- 

 ber, and while the decaying wood in which they lived was somewhat 

 damp, yet the percentage of moisture was low. 



INTERNAL CHARACTERS 



Brain. — ^This organ (PI. X, Fig. 35) occupies a median dorsal po- 

 sition in I and II, being chiefly in the latter. Both anterior and 

 posterior margins are convex; the lateral margins converge cephalad. 

 The average of a number of measurements shows that it is about 

 twice as long as wide. These two dimensions differ somewhat in 

 different specimens, but the ratio is nearly uniform. A fairly rep- 



