PACIFIC COAST OLIGOCH^TA. 143 



somites, then clianges into a narrow keel. This in the largest specimen, all having 

 been slowly killetl and straightened out. 



Clitellum unknown, all specimens being immature. 



Genital 'porc^. Two pairs of s/)ermathecal pores between ix-viii and viii-vii, in 

 front of the respective septa, the spermathecic thus being in ix and viii. The pores 

 are in line with setic 1 and 2, but are not prominent. Ovidacal pores are in front of 

 sette 1 and 2 between xii/xiv. 



Prostate /)ores in two pairs in the center of somites xvii and xix, in line with 

 setjc 1 and 2. But each pore is really a duplex of two joint pores, which are only 

 separated at the very epidermis by a thin wall. Thus the two prostates of each 

 couple run parallel through the body-wall, each one opening separately, but the pores 

 being so closely joined that they appear almost as one. No setag of any kind near these 

 pores (figs. 151 and 152). 



Spermiclacdl pores are seen in line with sette 1 and 2, close posterior to the 

 sette, only visible by strong transmitted light. The genital region in my immature 

 specimens did not show any particular structure with papilhe, etc. The median fossa 

 already referred to causes these pores to be situated on a slight ridge, which was not 

 marked off laterally. Close to each prostate pore on their ventral side is a small 

 tubercula piibertatis, only visible in sections. 



Fenial sctic absent. 



Common setre. Strictly paired ventral and lateral; 3 and 4 being situated 

 slightly ventral, below the horizontal line. Setae 1 and 2 are missing in somites xvii 

 and xix. In xviii the ventral setfe 1 and 2 are present, but do not differ from the 

 other sette, which are all plain and sigmoid. 



Kephro2)ores in front of sette 3 and 4. 



INTERNAL CHARACTERS. 



Bodij-wnU offers no prominent characteristics, except that the peritoneal layer 

 is enormously developed in all somites posterior to xiii. Peritoneum is strongly vas- 

 cular, but in addition to the usual small peritoneal cells we meet with a thick layer 

 consisting of a single row of tall peritoneal cells of varying but fairly even height. 



Peritoneal cells are in places as high as the other layers of the body-wall com- 

 bined, while in other places they are shorter. Similar peritoneal cells cover also the 

 septa, principally those posterior to xiii. The center of the septa bear as a rule the 

 tallest cells (figs. 149 and 153). These cells show a round nucleus and a granulation 

 which resembles that of chloragogen cells, but which does not stain deeply as does 

 the one of the latter cells. 



The heaits in x, xi and xii, as well as the septal glands in vii and viii, are also 

 surrounded by similar cells. The dorsal blood vessel again is covered by regular 

 chloragogen cells. 



Septn. Those separating respectively somites v to xii are slightly thickened 

 and very strongly cupped, but not covered by any peritoneal cells. The septa sep- 

 arating xii to xiv are less cupped, not thickened, but all covered by a few peritoneal 



