380 Mr. H. A. Baylis on Inlialitants of 



assert that Gecarcoidea lalandii, tliough apparently a more 

 land-loving species, never enters fresh water. 



In any case, however, whether the eg'gs were deliberately 

 deposited in or near the gill-chambers by the female fly, or 

 whether the larvai subsequently wandered into them, either 

 accidentally or following some regular instinct, they would 

 appear to have thriven there, and it is suggested as at least 

 a possibility that they derived sustenance from the blood of 

 the crabs, their chitinous "jaws" enabling them to puncture 

 the epithelium of the gills or of the vascular lining of the 

 chamber. 



With regard to tlie Oligochsete worms, the case is even 

 more puzzling, as they have not even jaws, and it is difficult 

 to see what food, except, perhaps, mucus, they can obtain in 

 such a habitat. The remarks made on this head concerning 

 Enchytrceus carcinophilus [2, p. 14] apply equally to the 

 present species, which I now proceed to describe. 



Enchytrceus parasiticus^ sp. n. 



This form is evidently very closely related to the species 

 (i?. carcinophilus) described by me from the gill-chambers of 

 Gecarcinus lagostoma [2]. It differs from it, however, in 

 certain features sufficiently to constitute a distinct species. 

 In size it is considerably smaller than E. carcinophilus, 

 measuring only 8-9 mm. in length, or about one-quarter of 

 the length of a iull-grown specimen of the larger species. 

 Its thickness is about 0*35 mm. The number of segments in 

 several specimens in which they were counted was found to 

 vary between 69 and 82. 



The chaeta? are arranged, as usual, in 4 bundles to each 

 segment, but there are invariably only 2 chaBtse in each 

 bundle; they are simple, pointed, and straight. Segments i. 

 and xii., as in the other species, are without bristles. 



There is a very marked ventral flexure of the anterior end 

 of the worm, the prostomium being bent down into a vertical 

 position, and the mouth being therefore quite ventral. This 

 peculiarity was not observed in E. carcinophilus, but in the 

 present species is so constant a feature that the specimens 

 invariably lie on their sides, and can only with considerable 

 difficulty be mounted in any other position. 



The clitellum is veiy feebly developed as compared with 

 the larger species. It is, in fact, very inconspicuous, but 

 can be made out as a very slight thickening, containing 

 glandular cells, extending from about the middle of seg- 



