1893.] PROSTATE IN THE OLIGOCH.13TA. 477 



genus Moniligaster " tlie prostates are formed by a metamorphosis 

 of certain peritoneal cells." The real equivalent therefore of the 

 " prostates " in the Limicolae and in Monilujaster are to be found 

 in the peritoneiuu of Acantliodrilus, Perichceta, &c. " In Earth- 

 worms therefore," I concluded, " there are two organs which have 

 been termed prostates — (1) the atrium of Acantliodrilus, Pericliceta, 

 &c. ; (2) the atrium + prostate of Moniligaster." 



These opinions were upheld with slight modifications in a subse- 

 quent paper (5, p. 117 &c.). One important difference between 

 the atria of the higher and those of the lower Oligochaeta 1 sought 

 to explain by the primitive position of the atrial pores. Assuming 

 that they originally were developed as invaginations of the clitellar 

 region, it would follow that the lining membrane would consist, as 

 does the clitellum, of two layers of cells ; the resemblance of the 

 cellular lining of the atrium in Acanthodrihis &c. to the clitellar 

 epithelium has been commented upon by others as well as by 

 myself. In the lower Oligochajta, on the other hand, the clitellar 

 epithelium is one-layered ; hence the lining membrane of the 

 atrium is one-layered also. My later discovery, made since the 

 paper to which I am now referring was written, that Moniligaster 

 has a clitellum like that of the lower Oligochajta, still further con- 

 firms this way of looking at the facts. In the lower Oligochseta 

 the atrial epithelium is ciliated — another difference as I then thought 

 it ; I have, however, lately found that in Eudriloides hrunneus (n. sp.) 

 the same ciliation at any rate partially occurs. I need not therefore 

 recapitulate my attempt to explain what is now not a difference 

 between the lower and higher genera of Oligochseta. Other points 

 in this paper will be referred to again. 



The views expressed in my pnjjers were controverted by Benham 

 (10). He points out in the first place a confusion of terms of 

 which I was guilty. Mr. Benham writes : — "Beddard takes up a 

 rather curious position in regard to the prostate of Moniligaster. 

 For him the peritoneal coat, outside the muscular wall of the 

 atrium, is the ' prostate ' and is homologous with the " Cement- 

 Driise" (or prostate) of Txihifex. Now this prostate in Tuhifex 

 has been shown by Vejdovsky to be formed by a proliferation and 

 outgrowth of the atrial epithelium at a certain point, which bursts 

 through the muscular wall of the atrium and projects into the 

 bod} -cavity. The atrial epithelium is derived from the epidermis, 

 so that the ' Cement-Driise ' is epiblastic ; whereas the glandular 

 covering of the ' atrium ' of Moniligaster, Stylaria, Rliynchelmis, &c. 

 is raesoblastic,- — it is in reality a modification of the peritoneal 

 cells. Hence Beddard would regard the epiblastic ' prostate ' 

 (Cement-DriJse) of Tuhifex as the homologue of the mesoblastic 

 covering of the atrium in Moniligaster ! " I did make this compa- 

 rison at first ; and it seemed to me to be justified by the curious 

 fact that in Tuhifex the Cemeut-Driise was not covered by peri- 

 toneum, the rest of the atrium being covered ; the disappearance 

 of the peritoneum at this particular point appeared to me to indicate 

 that possibly the data of Vejdovsky were not perfectly accurate. 



