[Proc. Rot. Soc. Victoria, 26 (N.S.), Pt. I., 1913.] 



Art. VIII.— 0?i Two New Specien of Chaetogaster. 



By olive B. da vies, M.Sc. 



(Government Researcb Scholar, Melbourne University). 



(With Piute IX). 

 [Read 12th June, 1918J. 



Introduction. 



Chaetogaster is a genus of small, transparent worms, living on 

 certain fresh-water snails, clinging to them by means of a posterior 

 Sucker, or as is sometimes found, crawling about right in the 

 pulmonary chamber, into which it has worked it way through the 

 pulmonary opening. 



It does not seem to be confined to any one species of snail ; I 

 have found it on species of Limnaea, Isidora and on Plaiwrhis 

 gilherti. 



On Planorhis it was quite abundant, and could be seen in the 

 pulmonary chamber. This is worthy of note, as Dr. Annandale 

 remarks of C. heyigalensis that he saw " in one instance, in an 

 aquarium in which snails were somewhat scanty, a solitary worm 

 attempting to establish itself on a Planorhis ; but the connection 

 was only temporary, not lasting for more than a few minutes. The 

 mouth of the shell in this genus is too constricted to be suitable 

 for the worm, which is generally gregarious." On the other hand 

 not only, as above remarked, did I find C. australis infesting 

 species belonging to three genera of fresh water snails, but in some 

 cases it even preferred Planorhis to either Limnata or hldora, when 

 all three were present in the one jar. 



The fact that the Australian Chaetogaster is found on these three 

 genera is noteworthy. In Europe it is found on TAmnaea, while 

 here it is found on Limnaea, Isidora and /^hmorhis. In the same 

 way in Fasciola the cercariae are found in Europe in Limnaea, 

 while here they are found in several different genera; there is a 

 question whether Fasciola has been introduced on some Limnaeae 

 and spread here to other genera, and the same question, from 

 analogy, may be raised with regard to Chaetogaster. 



According to Beddard the genus Chaetogaster belongs to the 

 Naidomorpha, a group of Oligochaetes which has already been 

 recorded from Europe, America and Asia (India); but as far as I 



