1918.] J. Stephenson: Oligochaefa of the Inle Lake. 17 



the case of the largest example ; the others are smaller, — one which is 

 only 98 mm. long and 2-5 to 3-25 mm. in thickness has well marked 

 male apertures though no clitellum. The largest specimen had 178 seg- 

 ments. 



The only notable difference of the specimens from the type is the 

 colour ; most species of Perionyx are distinguished by a rich purple 

 colour dorsally, and the fact that the type specimen was yellowish brown 

 and almost unpigmented suggested the specific name. The present 

 examples however are a deep brownish purple above, j)ale below. The 

 aquatic habitat is interesting. 



An immature Perionyx was also obtained from the Inle Lake, Southern 

 Shan States, from black mud at the edge of the lake, in about one foot of 

 water where much decaying vegetation was present. The locality, and 

 the fact that it was also aquatic, suggest that the specimen belongs to 

 the same species ; and this is borne out to some extent by the com- 

 mencing change in the male area, where the transverse grooves before 

 and behind the male apertures, characteristic for P. fulvus, are beginning 

 to appear. I mention it because of its colour, which seems to represent 

 an intermediate condition between the fulvous and purple. To the naked 

 eye it appeared a dusky purple dorsally in the anterior part, becoming 

 increasingly lighter behind, and in the 

 posterior half it is merely buff or tawny. 

 Under the binocular dissecting micros- 

 cope the colour is uniform at the anterior 

 end ; but behind this, longitudinal 

 streaks of pigment are seen in each 

 segment, purple on a yellow background, 

 interrupted by the intersegmental furrows 

 and not always corresponding in position 

 from one segment to the next ; the streaks 

 are still present, but increasingly lighter, Fig. 5.— Perionyx fulms (presum- 

 up to the hinder end, but there they only fn ^which pigmeX'tion 



suffice to modify the yellow background develops, 



to a buff tint (fig. 5). The deposition of 



pigment thus appears to take place in streaks, and not uniformly, a 

 uniform tint being produced by expansion and coalescence of the streaks. 



REFERENCES TO LITERATURE. 



1. Annandale, N.— Notes on an Indian worm of the genus Cliaeto- 



gaster. Journ. and Proc. As. Sac. Bengal, n. s. vol. i, 

 1905. 



2. Beddaed, F. E.— a new Branchiate Oligochaete {Branchiura 



sowerbyi). Quart. Journ. Mic. Sci., n. s. vol. xxxiii, 

 1892. 



3. Davies, Olive B.— On two new species of Chaetogaster. Proc. 



Roy. Soc. Victoria, n. s. vol. xxvi, 1913. 



4. Dehoene, Lucienne— Les Naidimorphes et leur reproduction 



asexuee. Arch. Zool. exp. et gen., t. Ivi, 1916. 



5. MiCHAELSEN, W.— Zur Kemitnis der Tubificirlen. Arch. Naturges- 



cliichte, Ixxiv, Jahrg., 1908. 



n 9, 



