369 



Mr. F. E. Bed dard has recently contributed two papers on the 

 subject, wherein he homologises those structures which are present in 

 many Earthworms and which have been usually regarded as »prostates«, 

 with the »atria« of the Tubificidae and other freshwater Oligochaeta. 

 My purpose is to give certain reasons for retaining the word »prostatetf 

 for these organs in Earthworms. 



1) The general idea of the word »atrium« is a chamber, into which 

 open other smaller chambers, or passages. For instance, we speak of 

 the »atrium« of the piscine heart, which receives the body veins; 

 there is the »atrium« of Amphioxus, into which the pharyngeal slits 

 open, and which communicates with the exterior ; in the Tunicates, the 

 »atrium« has a similar relation; and so on. 



2) Claparède used the word in the same sense as Vejdovsky 

 does, to mean the dilated terminal portion of the spermduct, which 

 communicates with the exterior, contains the invaginable penis sheath, 

 and into which the »cement gland« pours its secretion. Vejdovsky 

 has shewn that it is formed by invagination of the body wall; is lined 

 by a layer of cells, which are sometimes ciliated : is provided with a 

 muscular coat, which in its turn is surrounded by a layer of granular 

 peritoneal cells (as in Stylaria, Tuhifex^ and others). 



c,. (r. 



Fig. 1. Tubifex: a atrium, h prostate, c spermduct, d pore of atrium i. 



3) What is the condition of things in the Earthworm? In Acan- 

 thodrilus, Pontodrilus and others there are cylindrical, more or less 

 coiled whitish structures in the neighbourhood of the spermiducal pores: 

 these organs are hollow, lined by epithelial cells, which are cubical or- 

 columnar, and non-ciliated : and surrounded by a thick coat of pear- 

 shaped cells containing numerous granules : closely resembling clitel- 



' In each figure, the atrial epithelium is represented as square cells : the pros- 

 tate or »clitellar« cells as pear-shaped granulated cells : the muscular coat by a thick, 

 black line : and coelomic epithelium as a row of dots. 



