626 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The stomach is large, and the intestine very small and short, opening 

 on the ventral surface of the body near the posterior end. 



C. bucinedax sp. nov. The body is a coriaceous, flattened sac, 

 minutely roughened over the whole surface, nearly as broad as long, 

 and about three-fourths as thick. The dorsal outline is longest and 

 strongly convex, the ventral being usually somewhat concave. The 

 cup is oblique, the ventral height being a little more than half the 

 dorsal. Its lower wall usually presents a shallow, longitudinal 

 cavity, so that the aperture is slightly kidney-shaped. The surface 

 of the cup is more delicately roughened than the body, and its edge 

 is minutely erose. In the average specimen the length of the body, 

 without the cup, was 0*016 inch, and its width 0*014 inch. 



This rotifer has no means of attracting its prey or bringing it 

 within reach, but depends wholly on such animals as chance to swim 

 into its oral cup. "When a Stentor or other animalcule of considerable 

 size enters the trap, the rotifer quickly pushes up the aperture and con- 

 tracts the walls of the cup upon it, until it is forced, with a sudden 

 slip, into the ample cavity of the pharynx. This apparatus enables it to 

 secure much larger prey than the usual ciliated structure ; but, in the 

 absence of locomotor organs, it can only live in water swarming with 

 suitable food. In the aquarium in which it was found it was living 

 almost wholly on the large Stentors. 



The author adds * as the result of a communication from Dr. J. 

 Leidy, that Dictyophora vorax described by him,f is evidently closely 

 allied and probably belongs to the same genus. The name is, how- 

 ever, preoccupied. 



E chino dermat a . 



Anatomy of Echinoids4 — R. Koehler finds that the Polian vesicle 

 of regular Echinoids has the structure of an excretory organ ; he 

 describes them as being, to the naked eye, of a light brown colour, 

 which is due to the presence of small brown lines which pass from 

 the middle line to the periphery of the organ, becoming wider as they 

 do so. The two layers of connective tissue, which form the walls of 

 the organ, are so united that the space between them consists of small 

 cavities, filled with special elements ; these last are cells with a very 

 distinct nucleus, and their protoplasm gives off fine prolongations, 

 which extend from one cell to another. In addition, there are 

 numerous granulations, arranged in masses and cubical cells, the 

 nature of which could not be made out. On the whole, there is much 

 resemblance to the excretory organ of Spatangus. 



The author describes the pedicellariae of Dorocidaris papillata, 

 and directs especial attention to the presence of the small gemmiform 

 ones on the buccal membrane, where they have never yet been 

 recorded. " Five very curious appendages " are described in con- 

 nection with the lantern of Aristotle, which are no doubt the gill- 



* Amer. Mon. Micr. Journ., iii. (1882) p. 151. 

 t Proc. Acad. Nat. Sci. Philad., ix. p. 204. 

 % Coroptes Kendus, xciv. (1882) pp. 1260-2. 



