88 TAMKOKNIA A<AI>KMV OF SCIENCES. 



iiaiiiiw excretory tube witli thick wiiUs. Nearest tlie iimli' pure this tube is quite 

 striiii:;ht, or only slii^htly foliled, I)ut at its distal end tln' wiiKlin^^s are greatly packed 

 or irrcf^nlarly coileil (fi;;. !'!*, tuln). 



The part posterior to the pcnial collar 1 have designated the atrinni proper, 

 simply because it does not contain any inner layer of glandular cells, and because in its 

 distal (Mil it connects with the true prostate. The excretory tube continues all through 

 this pari and is, so to say, suspended in a more or less dense ma.ss of fibrous tissue. 

 Nearer the collar this nui-ss is reduced to a few strands oidy, but towards the distal end 

 it becomes quite den.se, especially so nearest the tube, while towards the periphery it is 

 nnich less dense ((ig. 02,/. /., fdjrous tissue;/, xl., fibrous strands). Fig. 100 repre- 

 sents a cross-section taken near the distal end; the tid^e is seen coile(| in the center, 

 while fibrous tissue connects it with the walls of the atrium. 



The exterior layers of the atrium are constructed very much as the same lay- 

 eis o| the prostate proper and the storage chamber. There are three layers which 

 are common to the two diflfereiit parts of the [)r()state. Interiorly a thin layer of eir- 

 cidar nuisclcs somewhat variabh; in thickness in difTeiciit parts, but generally tjnly 

 three or four strands thick. Exterior to this layer runs a spirally wound layer of lon- 

 gitudinal muscles, arranged in band-like plates, and when seen in cro.s.s-section re- 

 sembling a row of fringes (figs. 100, 101, 102, 103, lOG, 107, /. m). Fig. 107 shows these 

 plates, highly magnified, to consist of rather rectangular muscular strands. Exterior 

 to this layer of I. m. muscles we find everywhere a broken row of prostate glands of 

 very minute size, appearing to [)enetrate in between the muscular j)Iates, though on 

 account of the macerated condition of the tissues I could not follow their tubes. These 

 small glands, which barely project outside of the muscles, are found everywhere from 

 the distal end of the storage chamber to the penial collar, wherever this muscular 

 layer is found. In places they are continuous, in others scattered about, seldom more 

 than one row thick (fig. 101, 7/s). Ihit as we reach the region of the narrow part of 

 tlu; |)roslate and especially the [)art of the storage chamber where the spermducts 

 enter, we find another thicker layer of prostate glands similarly scattered over the 

 longitudinal muscular fringe (figs. 102, 103, 10(>, 107, ///•. ///. s, small pro,state glands; 

 pr. (ft. /., large prostate glands). In the region where the spcimducts enter the stor- 

 age chamber this layer of large prostate cells is almost continuous and considerably 

 thicker than the muscular layers combined (fig. 103). 



The prostate proper contains besides these layers of muscles and exterior 

 prostate glands two inner layers, which resemble and propably correspond to the two 

 cell-layers found in the prostate of the higher oligoclweta, viz.: one layer of lining 

 epithelium (fig. 101) and one layer of glandular pro.state cells, with veiy large nuclei, 

 and separated one from the other by transparent spaces, through which possibly enter 

 projections of the exterior prostate glands. These two characteristic layers do not 

 extend to the narrowest part of the pro.state. Hence tlu' nuiseular layer is covered 

 by a single row of inner lining epithelium with large, slightly oblong nuclei (fig. 

 102), whicli in the very inirrowest part are about 12 to 14 in the row. 



The proximal end of the storage chandxi' is lined by a very thick I'pitludium 



