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Show 1 9 0 4 .] EARTHWORMS FROM NEW ZEALAND. 2 5 9 which these four species have in common, and in which they agree with Tolcea, is the coexistence in the posterior segments of meganephridia and micronephridia. Let us turn to Beddard's conception of the limits of the genus Megascolides ( = JVotoscolex FI.) and Cryptodrilus Fletcher (the history of which is well given in his Monograph, pp. 445 et seq.). He draws attention to the fact that in nearly all the worms described by Spencer, and in a considerable number of those described by Fletcher (at any rate in such cases in which sufficient information is given to enable a comparison to be made), there is a correlation between certain of the internal organs (p. 447), viz. that " they have either (1) paired nephridia, tubular spermiducal glands, and last pair of hearts in the 12th segment; or (2) diffuse nephridia, lobate glands, and last heart in the 13th segment." He decides to regard those species with the first set of characters as belonging to the genus " Jlegascolidesand those with the second group as " Cryptodrilus." He admits that there are exceptions to these correlations. It thus comes about that Michaelsen uses the generic name Megascolides for " micronephric," whereas Beddard employs the same name for " meganephric" worms. But the meganephric species are placed by Michaelsen in the genus Plutellus, which is thus extended to include species previously attributed to Argilophilus of Eisen, Megascolides of various authors, Cryptodrilus of Fletcher, as well as Plutellus of Perrier and Benliam. Thus we have this unfortunate confusion in the employment of generic names:- Megascolides M‘Coy, in Michaelsen's sense, = JVotoscolex (part) Fletcher, = Cryptodrilus (part) Beddard ; JVotoscolex Fletcher, as used by Michaelsen, = JVotoscolex FI. 4- Cryptodrilus FI. = Megascolides (part) Spencer ; Cryptodrilus, in Beddard's sense, = Cryptodrilus Fletcher, = Megascolides (part) Spencer, = JVotoscolex (part) Fletcher ; Megascolides, in Beddard's sense, = Cryptodrilus (part) Fletcher, Spencer, = Megascolides (part) Spencer, = Argilophilus Eisen, = Plutellus Perrier. It is natural that in a group like Earthworms a mixture and confusion of this sort is likely to arise as knowledge advances; and it remains for Prof. Baldwin Spencer with the large stock of material in his possession, to endeavour to find some more satisfactory method of discriminating between genera than those usually employed. Of course the correct name that should be applied to the genera 17* |
