C. ROUSSELET ON A METHOD OF PRESERVING ROTATORIA. 209 



Pedalion and the various species of Brachionus, Anurea, 

 ]S^otliolca, and similar forms offer no diflB.culty. Limnias 

 ceratophylU stretches as far as it can out of its tube under the 

 action of cocai'n, but then contracts slowly and becomes opaque 

 before dying; the fixing solution must, therefore, be added 

 before the contraction begins, and when the cilia are still in full 

 motion. 



Floscularia aud Melicerta are very sensitive to cocai'n ; add 

 little to the water and fix before the cilia have ceased to move. 

 After having been under the influence of cocai'n they will not 

 contract when killed quickly. 



Stephanoceros is excessively sensitive to cocain, and only a 

 trace of it can be added to the water, under the influence of 

 which it must remain for a long time (hours) before it can be 

 killed. The long cilia on the arms seem to retain their vitality 

 the longest, and are thrown in violent and utmost confusion by 

 a little too much cocain, even when the animal is no longer 

 able to retract into his tube. 



The soft bodied forms of the genera Philodina, jS'otommata, 

 Furcularia, etc., are more difficult of treatment, and as they are 

 not generally found in numbers, experience in their preserva- 

 tion can only be gained very gradually. 



With some Rotifers, especially Euchlanis, T have had no 

 success, whilst I have not yet had an opportunity of experi- 

 menting on a number of other species. 



I trust, however, that the indications given in this paper 

 will enable many, after gaining a little experience, to preserve 

 the new or interesting forms they may meet with, and that 

 eventually it will be possible to make a complete collection of 

 type specimens of the Rotifera. 



