AN ATTEMPT TO CLASSIFY EARTHWORMS. 207 



states and the " atrium/^ or enlarged part of the sperm-duct of 

 T u b i f e X, into which the cement gland opens ; and in his various 

 papers on earthworm anatomy uses " atrium " to signify the 

 prostate of authors^ and by " prostate " refers to the peritoneal 

 (? glandular) covering of the terminal portion or '' atrium " of 

 Moniligaster and Stylaria. 



I will not, here, enter into a discussion of this subject ; I 

 shall, however, reject "atrium," and retain the older word 

 "prostate" for these glands, which either pour their 

 secretion into the sperm-duct, or open, independently, to the 

 exterior. 



This prostate is a hollow structure, the wall of which is 

 formed of club-shaped cells similar to those found in the 

 clitellum : sometimes, a layer of columnar epithelial cells 

 intervenes between the clitellar cells and the lumen ; some- 

 times the columnar cells are absent. A layer of muscles 

 usually surrounds the clitellar cells ; or the muscular layer 

 may be confined to the proximal region of the prostate. 



In many cases, as in Perichseta, Pontodrilus, Eudrilus, 

 &c., the prostate opens into the sperm-duct, so that we only 

 have one "male pore." In other genera, as in Acantho- 

 drilus, Deinodrilus, &c., the prostates open to the exterior 

 independently of the sperm-ducts : in these cases we must dis- 

 tinguish "spermiducal pores" from "prostate-pores." 



The word " spermatheca " is retained, in preference to the 

 " receptacula seminis " of other authors. 



The glandular structures met with in Lumbricus, Peri- 

 chseta, Brachydrilus, and others, and usually called "cap- 

 sulogenous glands," are misnamed. As far as we know they 

 have nothing to do with the formation of the capsule or 

 cocoon, which is formed by the hardening of the secre- 

 tion of the gland-cells of the clitellum ; but they give rise to 

 the albuminous fluid found in the cocoon, in which the ova 

 and spermatozoa are deposited, and which serves as nourish- 

 ment for the developing embryos. Vejdovsky suggests the 

 word "albumen-glands" for these structures, a term which 

 I retain. 



