PACIFIC COAST OLIGOCH^TA. 85 



connecting the former with, third, the posterior one, a storage chamber for sj)erm- 

 atozoa. 



Sperrnduds are two pairs, exceedingly narrow, opening close together in the 

 posterior part of the storage chamber. 



CiJutled rntfetfeft, two pairs, the anterior pair opening in ix. The posterior pair 

 in X, both in front of the septum. They are exceedingly thin and flat. The posterior 

 wall is attached to the septum. 



Sperm-sacs consist of a pair of very long continuous sacs, which cover the 

 generative organs, including the spermatheca, and extending from somites x to xvii 

 or xviii, generally several somites posterior to the caudal part of the storage chamber. 



Setce are 8 in 4 pairs in each somite, commencing with the second. 



The vascular systein is characterized by blind forked vessels in the posterior 

 30 odd somites, thus bringing the genus in close relationship with Lumbriculidse. 

 Another characteristic is the two loops of lateral vessels which branch out from the 

 main vascular trunks in somites ix and x, and which run backwards as far as the end 

 of the storage chamber. The anterior eight somites contain winding lateral vessels 

 connecting the two main dorsal and ventral trunks. Hertzkorper in the dorsal vessel 

 as well as in the branches in the intestine. After these preliminary references to 

 the main anatomical points I will enter more fully upon the anatomical and histo- 

 logical structure of the various organs. 



Bodij-vmll and ClUdlmn. The finer structure must be left for future study. 

 The inner longitudinal muscular layer is considerably thicker than the transverse 

 layer and hypodermis together. The longitudinal strands are very thin and ribbon- 

 like, some being much longer than others and reaching through the width of the 

 layer, others being very much smaller, situated principally close to the transverse layer. 

 Figs. 77, 79, 99, etc. 



The clitellum comprises about 6 somites, commencing in the posterior part of 

 ix and extending to the center or posterior part of xiv. The clitellar glandular 

 cells, one layer thick, are oblong, irregular, flask-like, containing very coarse, angular, 

 grains (fig. 79). They are separated or interspersed by large non-staining cells. 

 The peritoneum is rather poor in blood vessels, but the layer is very thick, in places 

 almost as thick as the longitudinal muscular layer (fig. 82, pr). 



Septa. None of the septa are abnormally thickened. The first distinct sep- 

 tum is seen between somites v and vi. The septa are straight, not cup-shaped. Those 

 surrounding the various divisions of the prostate are much firmer than the others. 

 They constrict the prostate, in fact the latter appears notched at every septum 

 (figs. 78, 92, 94). 



Alimentary canal. The alimentary canal can properly be only divided in two 

 parts — pharynx and intestine. The pharynx which ends in somite v is developed 

 latterally and dorsally, but not ventrally (figs. 83, 77). The thickened part is very 

 thick, consisting of the usual narrow and almost filiform cells. The ventral part is 



