PACIFIC COAST OLIGOCH^TA. 157 



INTERIOR CHARACTERS. 



Septa. Thickest septum is found between somites xi/xii. Anterior septa are 

 gradually diminishing in thickness forward, and similarly the septa posterior to xi/xii 

 are diminishing in thickness backwards. The most posterior thickened septum, the 

 one between xiv/xv, is hardly thicker than the one next posterior. The central 

 part of the thickened septa is very much thicker than the part near the body-wall, 

 (fig. 127 t.m.) The septa correspond more to the intersegmental grooves than do those 

 in Sp. Benhnuii. When the body is viewed in cross-section it will be seen that the 

 septa are principally attached to the body-wall at four points nearly half way between 

 the setae (fig. 131). 



Suprapharyngeal and septal glands. There are dorsal septal glands in iv, v, 

 vi, vii, about equal in size, and ventral septal glands in v, vi, vii, also of about equal 

 size. The latter are much larger than in tSjjarganophilus Benlianii, and reach above 

 the center of the body (fig. 120). In addition to these glands I find an accessory 

 septal gland attached to the central anterior surface of septum ix/x, just above the 

 intestine and extending downwards. This gland is closely attached at every point to 

 the septum, and projects onl}' slighth' into the ccelomic cavity. In height this gland is 

 not much thicker than the central part of the septum (fig. 132). Its free surface is very 

 smooth and even. I could follow ducts with precipitated secretions running along the 

 septum downwards towards the intestine, but its coimection with the latter, if any, I 

 could not ascertain. Beddard suggests that as the nephridia only commence in the 

 thirteenth segments the septal glands described by Benham in Sp. tamesis are homo- 

 logous with the nephridia. In all species of Sparganophilus investigated by me I find 

 no such raucous glands as in Pontoscolex, only regular salivar}- glands, which open 

 into the pharynx, and of the same structure as the supra-pharyngeal glands generally. 

 These salivary glands in 8p. tamesis occur exactly in the same somites as in all other 

 Sparganophilus species, viz.: iv, v and vi. 



Body-ivall offers no other characteristics, except that it is tliroughout of almost 

 the same thickness, and not thinner along the dorsal parts of some of the central 

 somites, as in 8p. Benhami. 



Clitelhun is continuous all around the body, but it is much thicker dorsally 

 than ventrally. This thicker donsal portion commences with the tubercula pubertatis, 

 gradually increasing in thickness dorsally towards the median line, where it is four 

 times thicker than at the ventral median line between the tubercula pubertatis. This 

 refers only to the clitellar cells in the central clitellar somites. The long clitellar 

 cells are confined to the latero-dorsal jjart, while the ventral part contains only 

 the short clitellar cells, the point where the former cease being the tubercula 

 pubertatis. This is the case in all the species examined by me. 



Ihihercula pubertatis. It has already been stated that they form a continuous 

 ridge, only broken in the anterior two somites xvii and xviii. Their structure differs 

 considerably from that of SpargnaophUus BenJiaim. We find the tubercle cells less 

 differentiated (fig. 138), and more resembling the short clitellar cells, of which they 

 are only a variety. Another characteristic is the presence of a large blood vessel in 



