STUDIES ON EARTHWORMS. 89 



points viz. in the possession of similar intestinal glands, and 

 of pyriform sacs. These led me at first to think that I had to 

 deal with an Urochseta, but the various points of difference 

 — e. g. the setae, which in Perrier's form are notched at the 

 free extremity, the nephridia, the character of the seminal 

 reservoirs, which are elongated and tongue shaped in Uro- 

 chseta, the presence of a distinct prostomium, which is not 

 the case in Perrier's worm, and the general character of the 

 alimentary tract, — all these lead me to form a new genus for the 

 worm under consideration. 



Diachseta Thomasii, nov. gen. et. sp. 



In a bottle containing several small worms from St. Thomas 

 (West Indies) some were very noticeable on account of their 

 stoutness and of the arrangement of the setse ; this latter pecu- 

 liarity suggested tome the name Diacheeta, since the setse are 

 far removed from each other as in Plutellus and Ac. mul- 

 tiporus, and moreover alternate from somite to somite, as in 

 the posterior region of Urochseta, and in Schmarda's genus 

 Pontoscolex. 



External Anatomy. — The worm is cylindrical with very 

 obtuse rounded extremities and is greatly swollen anteriorly, 

 instead of narrowing towards the prostomium (PL VIII, fig. 

 22). Its length is about 3 inches, and its breadth about ^rd 

 inch, but the worm was very much contracted so that these 

 measurements will not represent its size when living. The 

 body consists of 335 somites, of which those behind the clitellum 

 are very short, whilst in the preclitellar region they are of 

 much greater length ; some of these anterior ones are traversed 

 by two grooves with a slight ridge between them, on which 

 the setse are placed (fig. 22). 



The prostomium is absent, and the anterior border of the 

 buccal somite is not much narrower than the clitellum. It is 

 marked by numerous longitudinal grooves extending back- 

 wards for about half the length of the somite. 



The clitellum extends through somites xx to xxxiii, and 

 completely surrounds the body (fig. 24), as in Perichaeta, 



