380 THOS. H. MONTGOMERY, 



Zone and an inner clear spot; sections show that this central clear 

 spot is not the opening of a pore or canal, but that it is merely a 

 core of lighter and less refractive substance, which is surrounded by 

 a darker and more deeply-staining peripheral layer. 2) Tubercles which 

 are usually of less than half the height of the preceding, and are 

 either heraispherical or of a rounded conical outline. These also bear 

 hairs upon their apices, but the hairs are less numerous and more 

 delicate than those of the preceding tubercles, and may be seen only 

 by careful focussing with the Immersion lens (^/i2 of Zeiss). 

 3) Hyaline processes which are not seen upon surface views, and 

 which are usually either club-shaped or finger-shaped; these pro- 

 cesses which may represent sense-organs, are always slender in form, 

 but may attain nearly the altitude of the first kind of tubercles. 



The tubercles of the first order are arranged into two kinds of 

 groups: 1) They occur in pairs, the two components of such a pair 

 being in close contact, while the longitudinal axis of the two lies more 

 or less in the transverse plane of the body. These isolated pairs 

 — which are occasionally represented by groups of 3 or 4 — are usually 

 placed at quite regulär distances from one another, and the tubercles 

 composing them are as a rule slightly larger than those which form 

 the next kind of groups. 2) The greater number of these tubercles 

 (of the first order) occur in groups of about 15 to 20, in which the 

 individual tubercles are not in contact with one another; the number 

 of these larger groups is not quite as great as that of the groups 

 of twos. The second kind of tubercles are the most numerous of all, 

 and are not arranged into groups. The third kind occur singly and 

 sparingly, and are the least numerous of all, though they are somewhat 

 more numerous on the ends of the body than elsewhere, especially on 

 the posterior end of the female. Cuticular tubercles are wholly absent 

 on the tip of the head. 



Form. In the male the body is cylindrical, the anterior end 

 gradually diminishing in diameter ; the head is small, obtusely rounded 

 at the apex, and narrower than the portion immediately preceding. 

 The posterior end of the body (for the length of three-eighths of an 

 inch) is narrower than the part preceding ; the distal end of body, as 

 seen on lateral view, is truncated, there is a slight ventral groove in 

 the median line, which extends from the distal end to the cloacal 

 opening, which is not terminal. Female of greater diameter and 

 length than the male; the posterior end of the body (for the length 

 of half an inch) is narrower than the part immediately preceding, 



