1887.] ANATOMY OF EARTHWORMS. 389 



turity. The fact that in Acanthodrilus those glands do produce ova 

 is, to my mind, a %ery strong confirmation of the correctness of Dr. 

 Bergh's interpretation. I would also recall to the recollection of 

 those interested in the group, the fact that Perionyx excavatus pos- 

 sesses occasionally two pairs of fully developed ovaries '. The corre- 

 spondence between the male and female glands in Lumbricidse is thus 

 closer than was at one time thought ; there are two pairs of testes 

 and two pairs of ovaries, although as a general rule only one pair of 

 ovaries arrives at sexual maturity. The occasional presence in Peri- 

 onyx of two pairs of oviducts, if it is to be regarded as a reversion, is 

 a further point of similarity. 



It is generally Ijelieved that the Oligochseta are to be derived from 

 ancestors resembUng in certain points existing Polychseta. One of 

 the essential points of difference between the two groups, so far as 

 we at present know them, is the limitation of the reproductive glands 

 in Oligochseta ; in the Polychseta there is an indefinite number of 

 reproductive glands, and most of the segments contain ovaries or testes; 

 in the Oligochseta terricola, on the contrary, the testes are limited to 

 two pairs^ and the ovaries to a single pair ; the occasional presence 

 of rudimentary or fully developed ovaries in the 12th segment is 

 evidently an intermediate step in the reduction of the generative glands. 



III. Note on the Genital Set^e of Perichceta houlleti. 



I have lately received, through the kindness of my friend Mr. W. 

 F. R. Weldon, a large number of Earthworms collected by him during 

 a recent visit to the Bahamas. The collection includes a species of 

 Eudrilus, probably identical with one of the species described by 

 Perrier from this quarter of the globe, and two species of Perichceta. 

 The Perichatae are referable to two distinct species, both of which 

 have already been described, but have not, so far as I am aware, 

 been recorded from the New World. One of these is Perichata 

 affinis, a species at present only known from India, China, and 

 Luzon ; it is interesting, therefore, to notice the occurrence of the 

 same species in the West Indies. The other is Perichceta houlleti, 

 recorded by Perrier from Calcutta and Cochin China, and by myself 

 also from the former locality. The structure of this species has 

 been described in some detail by Perrier ^, but his memoir contains 

 no account of the peculiar modification which the setae upon the 

 clitellar segments undergo. 



The specimens at my disposal were not in a fit condition for 

 section-cutting, owing to an accident during their transit ; but this 

 was the less to be regretted, as the softened integument allowed the 

 cuticle to be readily stripped off, and the setsB from different parts 

 of the body to be examined ; this usually cannot be done in well 

 hardened examples. 



The setae, which are, of course, disposed in a continuous ring 



• P. Z. S. 1886, p. 308. 



* In the Limicolse the testes may be much more numerous. 

 ' Nouv. Arch. d. Mus. t. viii. (1872). 



