364 OLIGOCHAETA 



A year after the publication of the paper just referred to I re-defined the genera 

 Perichaeta and Megascolex in consequence of the discovery that my Pleurochaeta was 

 identical with M. coeruleus. The definitions were as follows : — 



Pebichaeta, Sghmabda. 



Syn. Megascolex, Auct. 



Depinitiobt. Setae generally arranged in a continuous row round tbe middle 

 of each segment ; elitellum occupying two, three, or four segments (XIV-XVIl). 

 Male generative apertures paired, and situated upon eighteenth segment of 

 body, which is always behind the elitellum ; genital papillae occasionally 

 developed in neighbouring segments. Female generative aperture single, and 

 wiJhin the elitellum, upon the fourteenth segment. Two pairs of testes, more 

 or less solid and compact, in segments XI and XII ; terminal portion of 

 vas deferens on either side connected with the duct of a large prostate 

 gland. Copulatory pouches varsdng in number from two to four pairs, and 

 provided each with a variously shaped supplementary pouch or pouches. 

 Intestine with a caecum on either side in twenty-sixth segment. 



During the last few yeai's a large number of species of ■' Perichaeta ' have been 

 described by Fletchek and Spencer in Australia. The principal characters of these 

 are shown in the table on pp. ^66, 367. 



This table shows that the majority of the species dealt with are referable to 

 the genus Megascolex as defined in this work; three species, viz. P. queenslandica, 

 P. darnleieribis, P. peregrina, are as clearly referable to the genus P. sensu stricto ; 

 ' they are all typical species of the genus Perichafita,' says Fletcher. 



Several species, e.g. P. attenuata, P. enormis, P. coxii, are remarkable on account 

 of the diminished number of setae on the anterior segments of the body; the anterior 

 half of the body would be, ^s Fletcher has pointed out, indistinguishable from 

 a Cryptodrilid if the posterior half were missing. I have thought that this important 

 character, which serves to link the Perichaetidae with the Cryptodrilidae (56) should 

 be regarded as being of generic value. I now think that this genus cannot be 

 retained, for the reason that worms with tubular spermidueal glands and paired 

 nephridia, as well as those with diffuse nephridia and lobate spermidueal glands, 

 have sometimes a reduction in the setae of the anterior segments. 



The species P. baJceri, P. barronensis, P. canaliculata, P. terrae mginae, and 

 some others, have paired nephridia and tubular spermidueal glands. In having 

 paired nephridia and tubular glands P. intermedia ( = P. 7iovae-zdandiae) differs 



