354 ALFRED GIBBS BOURNE. 



P. breviseta grows to a larger size than the other species 

 of Pristina, and contains a greater number of segments, 

 and differs from them besides in two or three well-marked 

 characters. 



The dorsal setse are of two kinds {V\. XXVII, figs. 14 and 15), 

 capillary setse and spear-shaped setse: the latter are peculiarly 

 shaped, and are bifurcated at the distal extremity. (Compare 

 with these Vejdovsky's figures of the dorsal setse in Naidium 

 luteum, and those figured by myself forChsetobranchus). 



The capillary setse are of about the same length throughout 

 the body, except that in the second and third segments they 

 are shorter (this is the character referred to by the name of 

 the species). 



Those of segment ii are about half, and those of segment iii 

 about three quarters as long as those that follow. 



The coelomic corpuscles are black and very noticeable. 



The most anterior nephridia are in segment ix. 



I have not hitherto found sexual individuals. The budding 

 takes place, as a rule, after segment xxii (i.e. n = 22), and 

 the newly budded head consists, as in P. equiseta, of seven 

 segments (i.e. z' consists of seven segments in the genus Pris- 

 tina). (See PI. XXVII, fig. 12.) It has been largely the 

 comparison of these two species of Pristina which has led 

 me to believe that, as stated on p. 338, n is constant (with a 

 few individual variations) for the species, while the number 

 of segments in the new budded head is constant in the genus. 



I give below a few examples, selected from the very large 

 number of specimens in which I have counted the segments. 



1. More than thirty segments, no budding. 



2. More than forty segments, no budding. 



3. More than forty-six segments, no budding. 



4. More than fifty segments, with a budding zone after seg- 



ment XX. 



5. More than fifty-five segments, with a budding zone after 



segment xxii. 



6. More than fifty-six segments, with a budding zone after 



segment xxii. 



