208 DE. W. B. BENHi^M ON 



it belongs to tlie segment ix. ; next, a pair of vessels going to the 

 gizzard itself leave tlie dorsal trunk immediately anteriorly to 

 the delicate septum viii./ix., and evidently belong to segment 

 Tin. The next blood-vessel (c) to leave the trunk lies in front 

 of the septum vii./viii. (quite in front of the gizzard). 



The arrangement of the vascular system thus bears out my 

 contention as to the locality of the gizzard, and it will be worth 

 while to examiue the distribution of the blood-vessels in this 

 region in cases in which the gizzard appears to lie in more than 

 one segment. Very little has been recorded by recent observers 

 on the arrangement of vessels in Perichteta ; it has become the 

 fashion to mention the last " heart " only. 



The generative organs present a considerable amount of 

 variability. The sjpermathecae are a pair in segment viii., 

 opening anteriorly (PI. 16. fig. 4:d). Normally the sac is 

 globular and smaller than the diverticulum ; and the latter is a 

 long cylindrical tube, highly muscular, more or less coiled or 

 undulating, and not dilated at the end. The duct of the sac and 

 the diverticulum appear to communicate in the substance of 

 the body-wall. In one specimen (" B ") the spermatheca was 

 much smaller ; the diverticulum smaller than the ovoid sac, and 

 evidently empty of spermatozoa : nevertheless this specimen 

 was larger than others in which the spermathecse were larger. 

 In another specimen opened ("A") the spermathecse were absent, 

 but in other respects the worm appeared fully developed. 



The spermiducal gland and copulatory apparatus present a 

 condition which, up to the present time, is unique, I believe, in 

 the genus. 



The gland itself, though subject to slight variation in size 

 and proportion, occupies segments xvii., xviii., and xix. It 

 consists, normally, of two great squarish lobes, distinctly sepa- 

 rated from one another (fig. 4 h). Each lobe is incised round its 

 margin with a few shallow notches : passing from each of these 

 two lobes is a narrow duct ; and the two unite to form the " penial 

 duct " {d, fig. 4 c). This is of considerable size and passes 

 directly mediad across the top of a great oval gland ulo-muscular 

 sac (J), which is nearly as long as the two lobes of the glands 

 taken together. Having reached nearly to the mediad or internal 

 margin of this sac, it bends sharply upon itself and runs along- 

 side its former course, but extends further outwards, viz. as far 

 as the outer edge of the spermiducal gland itself. This recurrent 



