374 Proceedings of the Royal Physical Society. 



Plantes examples of Perichccta are at least as numerous as 

 of Lumhricus, and the gardeners have noticed them on 

 account of their much more active movements.^ 



The setse are arranged in a rather peculiar fashion, inter- 

 mediate between the arrangement described by Lankester in 

 A. kergnelenensis and that which obtains in the other species 

 of the genus. In the anterior region of the body, to as far 

 back as about the 20th segment, the setse are disposed in 

 the following fashion. On either side of the ventral median 

 line is a single pair of closely approximated setse, and 

 more laterally another pair on either side. Of this pair, 

 however, tlie two setse are much more widely separatea 

 from each other. In the hinder portion of the body, com- 

 mencing after the male generative orifices, the setse of the 

 ventral pair get farther apart from each other, but are 

 never so widely separated as those of the more dorsal 

 pair. 



Close to the anterior marmn of secrments 8 and 9 are the 

 apertures of the four spermathecse. Their position corre- 

 sponds to that of the segmental organs, being in front of the 

 ventral (innermost) pair of setae. 



On the 17th and 19th segments respectively are a pair of 

 apertures, situated each upon a circular flattened area, differ- 

 ing somewhat by its greater opacity and whitish colour from 

 the surrounding integument. These are the openings of the 

 vasa deferentia, and like the copulatory pouches they corre- 

 spond to the inner pair of seta^. Upon these two segments 

 the ordinary setae are replaced by the long curved penial 

 setae, the points of which protrude through the apertures. 



Of the nine or ten specimens that I had at my disposal 

 not a single one was fully mature ; the clitellum was entirely 

 undeveloped, and there were no indications as to its posi- 

 tion. Several of the segments — in one specimen as many 

 as six (segments 7-12) — are provided with a pair of genital 

 papillae. 



Body cavity. — The mesenteries separating the segments 

 from each other are especially well developed in the anterior 



1 Perrier, Arch, de Zool, Exp., vol. ix., p. 237, note. See also Baird, 

 P. Z. S., 1869, p. 40, for similar habits of Ferichceta diffringnis. 



