476 iTR. F. E. BEDDARD OX THE ATRIUM AXU [Mav 16, 



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

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

 the glands described by Perrier in Fericha-ta, Acanthodrilus, and 

 Diyasttr are possibly the equivalents of what he (Vejdovsky) terms 

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

 in Eudrihis which Perrier called " vesicula seminalis "' is to be 

 looked upon as the homologue of the atrium in the aquatic 

 Oligochaeta ; so also is the gland in Pontodrilus. 



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

 (4) that the genus MonUi^/aater — an earthworm according to the 

 definition of most naturalists — has a terminal gland connected with 

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

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

 prostates of Earthworms in general, giWug reasons for regarding 

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



Among Earthworms there are two principal forms of " prostate " 

 met with. In Acunthodnlvs, Pontodrih(S, and other genera tbe 

 glands are represented by long tubular bodies ; in Perichceta &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 ; tbe next question was whether these glands were homologous 

 with any structure in the lower Oligochaeta. As to the first ques- 

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

 from the branched gland of Perichaia 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 tbe sperm-duct in EudriJus. 

 Perrier's account of tlie 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 Eudrdus differs from that of Acantliodrilus, which is 

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

 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 Ev.drilus and Pontodrihis ; 

 the only difference concerns the thick muscular coat of the gland 

 in Evdrilvs ; but I pointed out that the genus Trirjuster 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 Eudrllus, 

 Tyi>havs, &c., leads to the inference that they are homologous ; 

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

 clearly fa\ours the supposition that it corresponds to the atrium 

 in the ' Limicolae. ' " The comparison of the gland of Perichceta 

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

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

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

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



