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Show 1887.] ANATOMY OF EARTHWORMS. 389 turity. The fact that in Acanthodrilus those glands do produce ova is, to m y mind, a very 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 possesses occasionally two pairs of fully developed ovaries '. The correspondence between tbe male and female glands in Lumbricidae 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 Perionyx of two pairs of oviducts, if it is to be regarded as a reversion, is a further point of similarity. It is generally believed that the Oligochaeta are to be derived from ancestors resembling in certain points existing Polychaeta. One of the essential points of difference between the two groups, so far as we at present know them, is tbe limitation of the reproductive glands in Oligochaeta; in the Polychaeta there is an indefinite number of reproductive glands, and most of the segments contain ovaries or testes; in the Oligochaeta terricola, on the contrary, the testes are limited to two pairs2 and the ovaries to a single pair ; the occasional presence of rudimentary or fully developed ovaries in the 12th segment is evidently au intermediate step in the reduction of the generative glands. III. NOTE ON THE GENITAL SET.E OF Perichata houlleti. I have lately received, through the kindness of m y 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 Perichata. The Perichata 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 Perichata 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 Perrier3, but his memoir contains no account of the peculiar modification which the setae upon the clitellar segments undergo. The specimens at m y 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 setae from different parts of the body to be examined; this usually cannot be done in well hardened examples. The seta., which are, of course, disposed in a continuous ring i P. Z. S. 1886, p. 308. 2 In the Limicohe the testes may be much more numerous. a Nouv. Arch. d. Mus. t. viii. (1872). |
