MR ROUSSFXET ON ROTIFERA. I97 



works a flagellum projecting into the underlying nephridial chamber. 

 They are distributed in groups of from 2 to 5 over the surface of the 

 nephridium. 



In Glycera (unicornis, Sav., siphonostoma D. Ch.) the ciHated 

 organ extends on the one hand to the body-wall, and on the other 

 into the open mouth of the nephridial sac, reaching to the extremity 

 of a blind outgrowth of this sac, which may be called its caecum. 

 Dead cells, solid excretory products, and waste debris of all kinds 

 accumulate in the sac by the action of the ciliated organ. Here 

 they appear to undergo dissolution, the soluble parts presumably 

 pass through the thin wall into the nephridium. Direct observation 

 and experiment seem to shew that the nephridium absorbs only 

 the soluble waste products from the ccelomic fluid. The function 

 of the solenocytes is perhaps the excretion of water. 



4. Note on Preserving Rotatoria. 

 By Mr Charles F. Rousselet. 



The object of this communication and demonstration, although 

 of very secondary importance, may yet interest some members of 

 this Congress, particularly those who take part in the biological 

 study of fresh water lakes and their microscopic inhabitants, in 

 which such great advances have been made of late years. 



I find that Ehrenberg already tried to make preparations of 

 Infusoria and Rotifera by allowing the animals to dry on a slip 

 of glass and covering them with a piece of mica ; in this way the 

 flat outline of contracted Rotifers was obtained, but the real shape 

 and internal organs of the animals were of course quite lost. Then 

 a common mode of preservation has been to put gatherings of 

 Rotifers in alcohol in which they contract to a shapeless mass and 

 many serious errors have been made in attempting to describe new 

 species from such material. 



Man}' attempts have no doubt since been made at preserving 

 Rotifera in a more natural condition with the result that up to quite 

 recently all text-books have pronounced this group of animals to be 

 unpreparable. 



Having taken up the study of the Rotifera some years ago, I 

 soon felt the want of type specimens which could be referred to for 

 comparison and for the identification of species. After many ex- 

 periments, extending over three years, 1 was successful in devising 

 a method by which most Rotifers can be preserved and mounted 

 as permanent objects in their natural form, fully extended, white 

 and nearly as transparent as in life, with cilia, muscles, nerve 

 threads and all tissues preserved in situ. 



I will not trouble you with the details of the progressive steps 

 by which this result was obtained, but will merely explain my method 

 and afterwards show you the results. 



