476 MR. r. E. BEDDARD ON THE ATRIUM AND [May 16, 



throughout the Oligochoeta (3, p. 143). The foUowhig is a brief 

 epitome of what he has said upou the subject : he considers that 

 the glands described by Perrier in Perivhceta, AcantJiodrilus, and 

 Digaster are possibly the equivalents of what he (Vejdo\ sky) terms 

 the " Cement-Driise " in the Tubificidse ; that the glandular tube 

 in Eudrilus which Perrier called " vesicula seminalis " is to be 

 looked upon as the homologue of the atrium in the aquatic 

 Oligochasta ; so also is the gland in Poniodrilus. 



The next contribution to the subject is by myself ; I pointed out 

 (4) that the genus Moniligaster- — an earthworm according to the 

 definition of most naturalists — has a terminal gland connected with 

 the sperm-ducts which agrees in all essentials with the atrium of 

 the aquatic genera. In a further contribution (5) I dealt with the 

 prostates of Eai'thworms in general, giving reasons for regarding 

 them as the horaologues of the atria of the lower Oligochseta. 



Amojjg Earth\\orms there are two principal forms of " prostate " 

 met with. In Acanthodrilus, Pontodrilus, and other genera the 

 glands are represented by long tubular bodies ; in Penchaia &c. 

 there are a pair of lobulate bodies often occupying the same position 

 with regard to the ends of the sperm-ducts. One question to be 

 decided was whether these two kinds of glands were related to each 

 other ; the next question was whether these glands were homologous 

 with any structuie in the lower Oligochfeta. As to the first ques- 

 tion, the tubular gland of Acanthodrilus was shown to differ only 

 from the branched gland of Perichata by the fact that the glandular 

 cells of which it is largely composed are in the latter segregated 

 into masses instead of forming a continuous coating. The answer 

 to the second question is rendered easier by a consideration of tlie 

 structure of the gland appended to the sperm-duct in Eudrilus. 

 Perrier's account of the structure and relations of this gland were 

 not, as I myself showed (6), quite accurate ; the sperm-ducts open 

 into the interior of the gland at about its middle. In this feature 

 the gland of Eudrilus differs from that of Accmihodrilus, which is 

 quite independent of the sperm-duct, or from that of Pontodrilus, 

 where the sperm-duct only opens into the gland near to its external 

 aperture. The identity of minute structure, however, appears to 

 favour a comparison of the glands in Eudrilus and Pontodrilus ; 

 the only difference concerns the thick muscular coat of the gland 

 in Eudrilus ; but I pointed out that the genus Trigaster of Benham 

 seems to be an intermediate form in this respect. "The iden- 

 tity of structure," I remarked, "between the glandular bodies 

 appended to the termination of the vas deferens in Eudrilus, 

 I'yplice^is, &c., leads to the inference that they are homologous ; 

 while the relations of the vas deferens to this body in Eudrilus 

 clearly favours the supposition that it corresponds to the atrium 

 in the ' Limicolaj. ' " The comparison of the gland of Pericliata 

 to the prostates of the Tubificidffi seemed to me to be rendered 

 impossible by reason of the fact that in the former the cells which 

 it was sought to compare Mere covered by the peritoneum, while in 

 the Limicolaj (I did not particularly mention Tuhifex) and in the 



