34 The Microscope. 



region (Plate I, fig. 15) between the caudal bifurcation and the 

 dorsal convexity, is narrowed and much more prolonged than in any- 

 other species, a peculiarity that seems characteristic. On account 

 of it the ovary appears to be unusually far forward, making the 

 oviduct uncommonly long. The oral annulus is not conspicuously 

 beaded. The oesophagus is not more than one- sixth the length of 

 the entire body. 



The size varies from j^j to -^^j inch. In the small form I 

 have seen an ovarian egg apparently almost ready for extrusion, 

 with the nucleus of another developing egg beside it. The 

 extruded ovum from the small variety, is entirely smooth, and 

 measures yfo" i^^^ ^^ length. 



This is an Icthydium, if the latter is to be considered a valid 



genus. 



3. Clicetonotus concinnus, sp. nov. — Plate I, fig. 6. 



The body is oblong, and the lateral margins more nearly 

 parallel then in any other observed species. The back and sides are 

 densely covered by small, hemispherical elevations or papillse, 

 ari'anged in oblique courses, and giving the animal a peculiarly neat 

 and attractive appearance. The two caudal glands are uncommonly 

 large and conspicuous. The ventral space between the two lateral 

 bands of locomotive cilia is entirely naked. The body is ^^ inch 

 long, and the egg, whose surface is smooth, measures j4^ inch long. 



4. Chcetonotus Slackice, Gosse.^ — Plate I, fig. 7. 



In this the characteristic part is the head, which is not lobed 

 but in outline (fig. 7) is like the half of a short ellipse, passing with 

 an abrupt angle into the neck, which is rather more slender, in 

 comparision with the body, than in Ch. larus, Ehr., which the 

 animal resembles in its general proportions. The upper surface is 

 conspicuously studded with quinquncial dots, this part and the sides 

 being also clothed with very fine hair, of moderate length, and 

 directed backward. The body is y^^ inch long. This form I have 

 not seen, and am therefore indebted to its discoverer for these* and 

 the following facts. 



It was in this species that Mr. Gosse discovered the water- 

 vascular system of the genus. In his specimens there were two 

 tortuous vessels visible on one side of the body-cavity, and one on 

 the other, all distinctly traceable, posteriorly, almost to the caudal 

 bifurcation, and anteriorly into the head, where each ended in a 

 clavate bulb. In the ventral region of the same part there were 



