Benham. — On Acanthodrilus ulieinosifs. 127 



& 1 



pairs of lobulated sperm-sacs (seminal vesicles) almost fill 

 the segments 11 and 12. Two pairs of conspicuous, yellowish, 

 coiled tubular glands lie in segments 17 and 19. These 

 are the " spermiducal glands " (or " prostates "). Each gland 

 is connected to the body-wall by a shining muscular duct, 

 which opens by the porophore seen externally ; the opposite 

 end of the gland is free. Each gland is accompanied by a 

 short muscular sac, containing the copulatory chastas afore- 

 said. When these are examined under the microscope the 

 sac is found to contain two or three chsetae, each of which 

 is long, delicate, hair-like, and gently curved, the tip being 

 somewhat spoon-shaped. 



[The functions of these parts is not known with certainty, 

 but in all probability the copulatory chsetae are inserted into 

 tbe spermathecae, serving to hold the worms together during 

 the process of copulation, and the secretion of the spermiducal 

 gland aids in this cohesion.] 



(b.) The Female Organs: There is the usual pair of ovaries 

 in segment 13, attached to the anterior wall, and behind each 

 is the funnel of the oviduct, a wide, flattish structure, resting 

 on the anterior face of the septum between the 13th and 

 14th segments; it leads iuto the short, narrow oviduct that 

 passes through the body-wall in the latter segment to reach 

 the exterior. 



There are two pairs of spermathecae (or copulatory sacs), 

 lying in segments 8 and 9 respectively ; each sac opens 

 to the exterior at the anterior limit of the segment, 

 through the pores already noted. The form of the sper- 

 mathecae is of considerable value in identifying the species 

 of our endemic worms. In A. uliginosus it consists of 

 an ovoid sac, the true "copulatory sac," reaching across 

 the segment, and free posteriorly ; it possesses a muscular 

 duct nearly as long as itself, into which opens a peculiar 

 " diverticulum," or accessory sac, which usually lies in the 

 preceding segment. This diverticulum* of the duct, which 

 alone contains spermatozoa — received from another worm 

 during copulation — is somewhat variable in size, but its wall 

 presents a considerable number of small rounded pustules on 

 its surface, so that it resembles in its entirety a blackberry. 

 Sometimes this diverticulum is flattened out (when empty) ; 

 at other times (when distended) it is more or less globular, 

 but always presents the blackberry-like form. The diverti- 

 culum is ''sessile," opening directly into the duct of the 

 spermatheca. [In a closely allied species, A. roses, it is 

 provided with a distinct stalk.] 



* The form of the diverticulum is one of the most readily recognised 

 specific characters in Acanthodrilus. 



