PACIFIC COAST OLIGOCHiETA. 87 



Spennntliecd. As stated there is one jiair situated in ix, the .sperniathecal pore 

 being posterior to the setae, and in line with the inner couples. The spermatheca 

 consists of two distinct parts, as is usual in this group, the lower muscular part, and 

 an upper rounded part consisting of an unicellular layer of dice-shaped cells. This 

 rounded chamber was sometimes situated in the same somite, ix, as the muscular 

 body, but frequently it projected backwards into somite x. 



The structure of this muscular part is represented in figure 82. The inner epithe- 

 lial layer, consists of narrow columnar cells, with rounded nuclei and striated proto- 

 plasm. Exterior to this layer, there is a thin one of transverse or circular muscles, 

 outside of which again is an epithelial stratum one or two cells deep, with slightly 

 oblong nuclei, the cells tliemselves being irregularly dice-shaped (fig. 82). 



Prodale and spetinducts. The most interesting, as well as the most complicated 

 structure of this species, is the prostate, of which I am now able to give a fuller ac- 

 count, which I believe will not leave any of the points of its structure in doubt. 



I have already referred to the three main divisions of the organ, the proximal 

 one consisting of a long cylindrical tube, containing penis, atrium and prostate. 

 Second, a veiy narrow tube of almost the same structure as the prostate part of the 

 former, connecting with a long cylindrical chamber of somewhat modified structure, 

 into which the two spermducts open, quite near its junction with the narrow part or 

 bridge. If we, however, disregard the diflference in size of these various parts and 

 only consitler the .structure, we find that the whole organ may also be divided in 

 three parts: 



First, the proximal part, which is entirely confined to somite x. This part is 

 npright, so to say, does not run backwards; it is also somewhat bent, forming a right 

 angle with the balance of the organ. This part consists of penis, and a long tubular 

 part which, in want of a better name, I designate as atrium (fig. 100 atr. and p.). 

 With somite xi commences a change of structure of this organ, common both to the 

 wide part and to the very narrow posterior part. I will refer to it as the prostate 

 proper, as it contains the thick layer of regular prostate cells so common in all higher 

 oligocha'ta where this organ occurs; it is the " two layer " — prostate of Beddard. The 

 third part or storage chamber is characterized by the absence of this layer. 



I will now refer to each one of these three or four parts in succession and more 

 in detail, beginning with the penis and atrium. 



Next to the body-wall, ending at the transverse muscular layer and from there 

 stretching inwards, is a reversible .sac — a preputium — consisting of epithelial cells, 

 with very large, round, compressed nuclei and striated contents. This epithelium is 

 surrounded by a thin muscular layer (fig. 100, pre., 101). 



Into this preputium opens a penial glans (fig. 100 p. qh., 101, etc.), consisting of 

 two separate covers, posteriorly attached to a collar of larger rounded or pear-shaped 

 cells, at the base of which are seen a number of muscular plates. This collar is 

 folded on itself, one part of the fold connecting with outer and one part with the 

 inner cover of the glans. Through the median line of these parts runs a long, very 



Memoirs, Vol. II, 4. February, 1895. 



