ZooL.-VoL. II.] RISEN— OLIGOCH^TA. 151 



The clitellum was not developed in the immature specimen 

 at my disposal. 



The -penial setce are without ornamentation, except for a 

 small fin-like flare at the very apex. The apex of one of 

 the setffi is furnished with a tiny hook, below which on the 

 curved side is situated the flare. The other setae is without 

 the hook but possesses the flare. 



Tne nefhridia are large meganephridia opening in front 

 of setae d. They are characterized by numerous — from 30 

 to 60 — minute crystals, probably of lime, strung out along 

 the whole length of the nephridium. Similar crystals, but 

 twice the size, are found in the sacculated intestine. None 

 are in the diverticles of the tubular intestine. The dorsal 

 part of each nephridium is covered by a ccelomic mantle 

 extending about one-third down the nephridium. 



The se-pta between VII and X are thickened both dorsally 

 and ventrally, but the septa between X and XIII are thick- 

 ened principally ventrally. ^ 



MICROSCOLECIN^. 



Key to the Species of Microscolex, Yagansia and Rhododrilus. 



A. Two pairs of testes. 



Micposeolex Rosa. 

 I. Two pairs of testes. No spermathecffi. 



1. No gizzard. Nephridia commence in V. Sperm-ducts join 



the center of the muscular part of the prostate. 



Microscolex dubius (Fletcher, 3). 



2. No gizzard. Nephridia commence in II. No septal glands; 



suprapharyngeal glands small. Sperm-sacs in XI and 



XII. Sperm-ducts join the prostate at the exterior pore. 



Microscolex Poiiltoni Beddard (38). 



3. Gizzard rudimentary. Nephridia commence in II. Septal 



glands small; suprapharyngeal glands large. Sperm-sacs 

 in XI and XII. Sperm-ducts join the prostate in the 

 body-wall, previous to entering exterior pore. Nephro- 

 pores with sphincter. 



Microscolex elegans (Eisen, 16). 



( 5 ) December 19, 1899. 



