BY VERA A. lUWlN-SMlTH. '00 



liave four rows. Of the Chrtosomatidcti hitherto described, three 

 species liave two rows: three species, three rows; and two 

 species, four rows. It has been suggested that these three types 

 should be placed in three distinct genera. 



The number of setae in each row varies in all cases with the 

 age of tlie animal, and is, therefore, not altogether a specific 

 character; but the relative extent of the body covered by the 

 rows varies considerably in the different species, as does, also, 

 tlie character of the setae. 



Two species have been described in which the seta3 are all 

 simple; in the others, either the setae are all compound, with a 

 small distal segment, or both simple and compound setae are 

 present. 



In all species, the part of the trunk on which the setae are 

 situated serves as a sole, the ventral setae become firmly attached 

 to some support; and the worm rears itself up and stretches the 

 anterior part of its body forward, when about to move. Schepo- 

 tieff states (7) that it then attaches itself, and draws itself 

 forward by means of mouth-teeth. But in all cases in which I 

 have been able to observe the C hcHtosomatidce alive, it is the 

 dorsal 'head-hairs,' or seta? arranged in a semicircle on the hinder 

 part of the rostrum, which perform this function. In the case of 

 N. tenax, I have been able to make out small, distal segments on 

 the dorsal setae, very similar to those on the ventral setae. The 

 adhesive power of these seta3 seems to be very great, and the 

 animal can only detach itself by a sharp jerk after each forward- 

 movement. 



The character and arrangement of the trunk-hairs varies con 

 siderably in the four New South Wales species. In Ck. falcatum, 

 they are so short and scattered as to be hardly noticeable; while, 

 in Ch. haswellij they are very long and prominent, and are 

 markedly swollen at the base. 



The internal organisation is simple. There is a body-cavity, 

 and the alimentary canal is a simple, straight tube extending 

 through the body from the mouth, at the anterior end, to the 

 anus on the ventral surface close up to the posterior end of the 

 body. A glandular mass, lying dorsal to the posterior end of 



