13 



OLIGOCHAETA. 



A PARASITIC ENCHYTRAEID. 



BY H. A. BAYLIS, B.A. 



I. General. 



Occurrence of a species of Enchytrseidse in tin' gill-chambers of a 

 Laud-oral) in South Trinidad ...... 



II. Systematic. 



Species referred to Enchytrceus diagnosis of A', carcinophilus, sp. n. 



III. Anatomical. 



External features ........ 



Internal anatomy ......... 



PAGE 



13 

 14 



15 

 16 



I.-GENERAL. 



THE "Terra Nova" was at the island of South Trinidad (Station 36, Lat, 20 28' S., 

 Long. 29 25' W.) from July 2(')-30, 1910. During this stay the opportunity of 

 shore-collecting was taken by the naturalists, and Surgeon E. L. Atkinson, R.N., 

 collected some of the Land-crabs (Gecarcinus lagostoma), which were taken alive on 

 board ship. On the 30th some of them were dissected, and their gill-chambers were 

 found to contain small worms, which were at first thought to be Nematodes. They 

 prove, however, to be typical Oligochsetes, and clearly belong to the family 

 Enchytrseidse. 



As records of Oligochaeta occurring in association, either as parasites or as com- 

 mensals, with other animals are by no means frequent, and more especially as only 

 one Enchytrseid appears to have been described as occurring in such association, the 

 fact of a member of this family having chosen such a situation is interesting. 



The one previous instance known to me is that of Pachydrilus \JEpitelphusci\ 

 catanenx/x Drago, occurring in the gill-chambers of the freshwater crab Telphusa 

 fluviatilis in Italy.* 



It is worthy of remark that the worm seems to have undergone no special 

 modification in structure as the result of its parasitic or semi-parasitic habit, but 



* I am indebted to Dr. R. T. Leiper for calling my attention to the preliminary account of this 

 species, in : Bull. Soc. Entom. Ital. Anno XIX., 1887, pp. 81-83. Drago's further account, with figures, in : 

 Ric. Labor. Anat. Roma, vii, Fasc. 1, IN'J'J, I have unfortunately been unable to consult. 



D 



