42 CALIFORNIA ACADEMY OF SCIENCES. 



considered as our largest earthworm, tliougli very variable, as might be expected. 

 The smallest adult worms measure about 1^ inches b}^ 8 lines, the largest again (5 

 inches by 4 to 4^ lines, the size appears to depend greatly on the locality and richness 

 of the soil. The prostomium divides somite i to about i or § (fig. 130). Somites vii, 

 viii, ix, are larger than the other anterior somites. The clitellar somites (figs. 125 to 

 lol) are large, the po.st-clitellar ones are very much smaller. The spermathecal 

 pores are more or less conspicuous (fig. 129 spth.), sometimes hardly visible, at times 

 again elevated and appeai'ing as small round rings. They are situated just lateral to 

 setfe 2, but of course in the intersegmental grooves between vii/viii aud viii/ix. The 

 ovipores are closer together, situated a little more ventrally than set?e 1, sometimes, if 

 not generally, connected by a depression. The clitellum is oidy developed dorsally 

 and laterally, the ventral part between the male pores being normal and appearing as 

 considerably depressed, in hardened specimens the depression reaching as far forward 

 as to the center of somite xiv or the ovipores. 



The male pores which open in line with seta3 2, are situated on either side on an 

 elongated papilla, which again is more or less surrounded by a circular depression, 

 outsiile of which is seen a high semi-circular ridge, which is thicker anteriorly and 

 posteriorly than laterally (fig. 25, 129). The penial seta' are one pair in each 

 ]iore, and are seen pi'otruding through the male-pore. 



The regular setie are sigmoiti, not greatly bent. The settc of the inner couples 

 are closer than those of the outer couples; all the setre are in jiarallel rows (fig. 24). 

 The nejihridio-pores are difficult to view from the outside. Their arrangement is 

 variable, but the majority are found outside of, oi' more lateral than the fourth row of 

 setfp. The three anterior nephridio-pores are seen in front of sette 4 (fig. 24). A 

 more tletailetl descrij)tion will be given further on. 



iSeffi. The ordinary seta^ have been alrea<ly described as sigmoid. There 

 are two sacs of penial setie attendant to each prostate, anil opening in the same pore, 

 but not in the same duct, as that organ. There is only one seta in each sac. This 

 seta is sickle-like, much moi"e curved than those in Deltania. The point is needle- 

 like, and curved (figs. 122, 123). The very point is void of sculpture, but the part 

 back of the point and up to the sac is sculptured as in the figure 123. The largest 

 part of the seta is smooth, only showing the rings for the attachment of the muscles. 

 The inner couples of seta? of the clitellum are somewhat raised, though otherwise not 

 differentiated. 



ANATOMICAL STRUCTURE. 



The body-wall (figs. 114, 115, IIG, 117, 118). The body-wall outside of tlie 

 clitellum shows the usual sets of layers. The innermost vascular layer, which covers 

 the longitudinal muscular layer, is very thick and prominent, though not very 

 crowded with blood vessels (fig. 114). Under this layer, and between it and the 

 longitudinal muscles, passes the spermduct, almost throughout its length, from the 

 place where the two ducts unite to the one where they rise to join the spermduct. 

 This layer is less pronounced anterior to clitellum, and appears absent in the vicinity 



