PACIFIC COAST OLIGOCHMTA. 143 
somites, then changes into a narrow keel. This in the largest specimen, all haying 
been slowly killed and straightened out. 
Clitellum unknown, all specimens being immature. 
Genital pores. Two pairs of spermathecal pores between ix—vili and yili-vii, in 
front of the respective septa, the spermatheci thus being in ix and viii. The pores 
are in line with sete 1 and 2, but are not prominent. Oviducal pores are in front of 
setee 1 and 2 between xii/xiv. 
Prostate pores in two pairs in the center of somites xvii and xix, in line with 
sete 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 sete of any kind near these 
pores (figs. 151 and 152). 
Spermiducal pores are seen in line with sete 1 and 2, close posterior to the 
sete, only visible by strong transmitted light. The genital region in my immature 
specimens did not show any particular structure with papille, ete. 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 pubertatis, only visible in sections. 
Penial setw absent. 
Common sete. Strictly paired ventral and lateral; 5 and 4 being situated 
slightly ventral, below the horizontal line. Sete 1 and 2 are missing in somites xvii 
and xix. In xviii the ventral sete 1 and 2 are present, but do not differ from the 
other sete, which are all plain and sigmoid. 
Nephropores in front of sete 3 and 4. 
INTERNAL CHARACTERS. 
Body-wall 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 
tullest 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 hearts 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. 
Septa. 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 
