PACIFIC COAST OLiaOCH.ETA. 71 



anterior se2ituni. In PlutnicodrUm taste, however, tlie spermatheca lies always flat 

 pressed against the ventral side of the body-wall, and is of sufficiently large size to reach 

 as far backwards as to the posterior septum between ix and x, which makes it about 

 equal in length to the diverticula of the (esophagus (fig. 1, spth.) The lower part 

 of the spermatheca is as usual more muscular than the free end, which in this species 

 is more or less, though always shallowly, lobcd, showing a large niunber of incipient 

 diverticula irregularly foruied and arranged. The spermatozoa are found [)riiicipally 

 in these warty diverticida. 



7t',s/es are vcr}^ long and situated as usual in x and xi. The posterior one at 

 least, and propably both pairs, coniiecit with the sperm-sacs in the same somite. 



jSjierm-sacs are arranged as in some species of Ocnerodrilus. They are all 

 paired. The anterior pair in ix is attached to the posterior septum of that somite. 

 This pair is ver>' much lobed, the lobes being more in number and in shape more 

 round than in any species of Ocnerodrilus, the pair resembling two bunches of large 

 grapes, completely filling the whole available space in the somite, especially above the 

 diverticula and the oesophagus. The sperm-sacs in x and xi are less or hardly lobed, 

 connecting with the the testes below, the latter, being long, slender and not branched, 

 reach across the somite and joining the sperm-sacs in the posterior part near the sep- 

 tum. The sperm-sacs in xii are connected directly with those in xi, but otherwise 

 attached to the anterior septum of somite xii. This pair of sperm-sacs are lobed but 

 not as much so as those in ix. 



There are two pair of ciliated rosettes in x and xi, and two pair of spermducts 

 as usual leading from them. The spermducts join, as is generally the case, forming a 

 single strand which runs close to, but a trifle more dorsally, than setse 2, until somite 

 xvii is reached. In this somite each spermduct enters a small muscular atrium devoid 

 of prostate, and entirely confined to the longitudinal layer of the body-wall. A.s soon 

 as entering the body-wall and this muscular chamber the two lumens of the spermduct, 

 which until now had been separate, fuse together and enter the muscular chamber as 

 one single duct. 



As atrium I consider a small muscular chamber entirely confined to the body- 

 wall, in wliich the spermducts open. This chamber is, however, devoid of any 

 glandular cell prolongation such as we are accustomed to find in Ocnerodrilus, and 

 ordinarily it ends where the spermducts enter, which is at the upper end of the layer 

 of the body-wall. The atrium itself consists of an inner layer of epithelial cells, 

 which at the very pore are much larger and furnished with larger nuclei, but which 

 gradually decrease in size as they approach the place where the spermducts enter. 

 This layer is a direct continuation of the hypodermal layer of the body-wall. An 

 outside layer again consists of fine muscular fibres with smaller nuclei directly con- 

 tinued from the transverse muscular layer of the body-wall. We see thus that this 

 short chamber might in reality be nothing but the remnants of a degenerated atrium, 

 or rather remnants of the lower muscular part of a degenerated prostate, which gland- 

 ular prolongation has disappeared. That this is the case I judge from the structure 



Memoiks, Vol. II, 4. February, 1895. 



