260 Transactions of the Society. 



another kind. It will be seen that there is much to be learned 

 by studying the mature and immature forms side by side. For 

 this reason it may be well, in the first place, to give the characters 

 of the young, then to describe the adult, and finally compare and 

 contrast it with the allied forms, in order if possible to determine 

 its position in the family to which it belongs. 



IV. — Cham^drilus chlorophilus g. et sp. n. 



Immature Forms. — Length from 5 mm. upwards, with twenty- 

 five or more segments, slender, thread-like, transparent. Setse 

 y-shaped, or sigmoid, present on girdle segment as elsewhere 

 during youth, slender, usually three per set, alike dorsally and 

 ventrally, never more, sometimes only two, equal in length, tend- 

 ing to become somewhat stronger behind than before. Tail very 

 sensitive. Kept in constant motion like the head for purposes of 

 feeling. No other external differences from typical Enchytrseid. 



Internally the septals at once arrest attention. Four large 

 roundish pairs in segments 4/5 to 7/8. In segment 8, attached 

 apparently to the posterior side of the septum of 7/8, an elongated 

 backward extending pair of glands. Brain narrowing anteriorly, 

 concave behind, longer than its greatest width, and attached to a 

 strong nerve-chain. A pair of club-shaped glands in the third 

 segment replacing the salivary glands, with duct-like processes 

 Tunning backwards beneath the septals. Chloragogen cells large, 

 oval when in situ, but becoming round when detached, and show- 

 ing sacs full of dark granular matter ; often dissolving somewhat 

 rapidly when the animal breaks up. Coelomic corpuscles large, 

 nucleated. At first any traces of a vascular system anywhere 

 difficult to be found. Later study by new methods showed the 

 dorsal vessel to be postclitellian, it being traced back in one case 

 to the 20th segment. Nephridia commence in segments 9/10. 



Mature Forms. — Length about 10-12 mm., but sometimes 

 stretching to 15 mm. when alive, and hardly contracting when 

 preserved. Segments varying from twenty-five to sixty-five or 

 seventy in number. SetiB never exceed three per set, even in fully 

 adult specimens ; length not exceeding \ diameter of body at most ; 

 wanting on girdle segment. Tail very sensitive as in youth. 

 Girdle on the 9th segment, but often extending to adjoining seg- 

 ments. Cells of girdle sometimes very indistinct, at other times 

 well formed. Sperm-funnel 2, 3, or 4 times as long as broad, 

 without collar, and attached to long slender duct, opening in seg- 

 ment 9 by almost invisible pores. Brain longer than broad, widest 

 at the posterior, which is incised. Four pairs of septal glands in 

 4/5 to 7/8, between the two last pairs of which a paired or unpaired 



