Anatomij and Histology of a New Earthworm. 61 



any rate its double heart, simple nervous system, the absence 

 of a subneural blood vessel, together with its sluggish habit, 

 mark Diplocardia as of low rank, and give us additional reason 

 for placing it in the lowest of the three recognized groups.* 



The two genera of post-clitelliani with which Diplocardia 

 has most in common are Acanthodrilus and Digaster, belong- 

 ing to Dr. Clauses family Acanthodrilidtt'. With Acantho- 

 drilus the genus here described agrees in the position of the 

 nephridiopore, in the possession of four groups of modified 

 seta?, in having four prostate glands, in the character and for- 

 ward position of the gizzard, and in the character of the 

 spermatheca?. 



Of the three species upon which M. Perrier based the 

 genus Acanthodrilus he says: "Leur caractere le plus saillant, 

 celui qui frappe tout d'abord, c'est Texistence de quatre orifices 

 genitaux males au lieu de deux. Par chacun de ces orifices, on 

 voit sailler un faisceau de soies courbes, d'aspect nacre, tres- 

 longues et plus ou moins retractiles, sans I'etre toutef ois d'une 

 maniere complete. Chacun de ses faisceaux constitue un veri- 

 table penis." In Diplocardia there are only two external open- 

 ings for the sperm ducts, and these are not upon the somites 

 upon which the pairs of prostates open (18 and 20), but upon 

 the intermediate somite (19). They do not pass into the pros- 

 tates and discharge the sperm through the ducts of the latter, 

 but can be traced from the somites in the anterior region of 

 the body, where they open into the body cavity as two separate 

 tubes, lying side by side in the inner muscle layer of the body- 

 wall until jast at the external aperture, where they unite in 

 one tube. The apertures are not accompanied by setae of any 

 kind, the inner pairs of setae being wanting on somite 19. 

 At the apertures of the ducts from the prostate glands on 

 somites 18 and 20 are long, gently and uniformly curved setee, 

 one ^;fnV for each of these ducts. They occupy the position 

 ordinarily occupied by inner pairs of setae, lie close together, 

 are perfectly smooth, very slender, and are capable of complete 



* In some of its characters it approaches tlie aquatic Oligochoita 

 limicolce. Eisen's Californian genus, Ocnerodrilus, is like it in the 

 separation of the two vasa deferentia of each side until the external 

 aperture is reached. Criodrilus approaches it in having an incom- 

 pletelj' double dorsal vessel. 



