| OCR Text |
Show 1886.] DR. A. G. BOURNE ON INDIAN EARTHWORMS. 663 I regret that in some cases I was unable to render my observations complete, owing to want of sufficient material. It seems, however, desirable to publish this preliminary note even though it is in some cases incomplete, as more thorough investigations in any particular locality may be considerably delayed. The greater number of forms belong to the genera Perichceta and Moniligaster, and for the present I deal with these only. I have found, in addition to these, two species of Lumbricus at great elevations at Ootacamund and Coonoor. One of these presents a clitellum extending over somites xxvii.-xxxiv., and the other over somites xxx.-xxxiv. I refrain from naming these until I can characterize them more fully. I have also some worms belonging to other genera, but with the scanty literature to which I have access 1 cannot say whether they are new genera or not. Had it not been for M r . B e n h a m V most useful rSsume of known Earthworms, I should have been able to do far less than I have done. Where I have given measurements or counted the somites I have chosen the largest individual I could find. PERICHJETID^E. The Perichaetidae are characterized by the fact that each somite bears numerous setae arranged in a more or less complete ring. The genera which are at present included in the group are :- Perichceta, Schm.; Megascolex, Temp. (Pleurochceta, Bedd.); Perionyx, E.P.; and Rhodopis, Kinb. These genera are at present distinguished one from the others, thus:- Perichceta presents a clitellum in somites xiv., xv., and xvi., a pair of laterally-placed male pores in somite xviii., and very numerous equidistant setae. Megascolex presents 100 setae arranged in a ring, but with a dorsal break. Perionyx presents a clitellum in somites xiii., xiv., xv., xvi., and xvii., a pair of male pores placed in a median pit in somite xviii., and 30 equidistant setae. Rhodopis presents a clitellum in somites xii. and xiii., a pair of male pores between somites xiv. and xv., and 50 to 60 equidistant setae. N o w let us consider these characters in relation to the worms described below. Among these we find that there are numerous intermediate conditions, in respect to the arrangement of the setae, between an almost equidistant series and a series presenting considerable dorsal and ventral gaps2. Secondly, in one form there are two pairs of male pores (P. stuarti). Lastly, with regard to the extent of the clitellum, in the form which I have referred to Perrier's genus Perionyx it extends over three somites instead of five, while among the 1 Quart. Journ. Microsc. Sci. vol. xxvi. n. s. 2 By the terms ventral and dorsal gaps I mean the space between the two most ventral and dorsal setae respectively. An ordinary gap is the space between any other two contiguous setae. |
