ZOOL.— Vol. II.] EISEN—OLIGOCH^TA. 105 



where the center of the typhlosole is occupied by two rows 

 of chloragogen cells. In our species of Pontoscolex the 

 blood-vessel occupies the central part of the typhlosole, 

 there being no trace of chloragogen cells. 



The blood-supply of the typhlosole is derived from the 

 dorsal vessel in two different ways, alternating with each 

 other in each somite. One of these methods of supplying 

 the blood is by a median, perpendicular vessel which dips 

 down from the dorsal median vessel into the typhlosole. 

 This vessel is very short. Besides this perpendicular ves- 

 sel, there are paired lateral vessels which start out sideways 

 from the dorsal vessel and alternate with the perpendicular 

 vessel (fig. 35)- They connect more laterally with the 

 blood-sinus of the typhlosole (fig. 36 a). 



Intra-typhlosolar Canals. — (fig. 36.) Throughout the 

 length of the typhlosole there exist in the upper part of this 

 organ a great number of internal ciliated canals enclosed by 

 a muscular investment continuous with the circular muscular 

 layer of the intestine. These canals, which are short, 

 occupy the part of the typhlosole situated between the 

 lateral and median vessels which supply the typhlosole with 

 blood, as previously described. In transverse sections 

 passing directly through, or in the immediate vicinity of, 

 these vessels, no intratyphlosolar canals are cut through; 

 but as we approach midway between these lateral and per- 

 pendicular vessels cross-sections of these canals come into 

 view. Generally there is but one canal, but there may be 

 two or even three parallel canals, of which one is larger 

 than the others. These intratyphlosolar canals originate in 

 the interior of the typhlosole, follow this organ in a parallel 

 line for some little distance, and then bend sufficiently to 

 open out into the upper part of the intestine at its junction 

 with the t5rphlosole (figs. 37, a, h, c). There is no connec- 

 tion between the canal and the coelomic cavity. 



These canals are all of the same uniform structure, — a 

 single row of cells with very large nuclei. The cells are 

 ciliated along the lumen of the canal and resemble those of 

 the sperm-duct. These canals probably serve as safety 



