1893.] MICROSCOPICAL JOUHNAL. 185 



external water, yet it can be done, and it has been done. In- 

 deed, I luive personally bad tlie satisfiiction of doing it. 



Students of this class of microscopic animals believe that the 

 endoplasm is everywhere pierced by exceedingly minute canals 

 which lead to the contractile vesicle, and pour into it whatever 

 they may have received. These more than microscopic chan- 

 nels cannot be seen, but that something, corresponding at least 

 in function to such canals, exists within the infusorial endo- 

 plasm. there can be no doubt. And if, even in the largest In- 

 fusoria, they are too minute to be seen with the best of modern 

 objectives yet do not fail in their function of carrying liquid to 

 the contractile vacuole, their invisibility is no argument against 

 the existence of minute pores in the extremities of the surface 

 villi on the contractile vesicles of the naked Khizopods referred 

 to. It is not making an unreasonable use of the imagination 

 to say, that the conduct of the contractile vesicles of Paramse- 

 chnn avrclia suggests exactly that interpretation. These vesi- 

 cles are normally sub-spherical; it is usually only when the an- 

 imal is in distress, or is pressed upon too heavily b}^ the cover- 

 glass, that they assume the stellate form with the branches ra- 

 diating from a central vacuole outwardly into thp endoplasm. 

 Is it not reasonable to suppose that the contents should then be 

 backed up into these ordinarily invisible channels to distend 

 them and to make them conspicuous? It is absolutely be- 

 yond a doubt that the Infusoria and other microscopic animals 

 have no more control over the pulsations of their contractile 

 vesicles than the human being has over the movements of his 

 OAvn heart. If the contrary was the case, there need not be any 

 undue enlargement of the vesicle, or any backing up of the vac- 

 uolar contents in these conditions of uncomfortable pressure, 

 or of uncongenial surroundings. 



No aquatic microscopic animal can swallow a particle of food 

 without at the same time swallowing a greater bulk of water. 

 It is an every-day occurrence to see an Infusorian engulf a 

 smaller, living animal, which is accompanied into the endo- 

 plasm by a comparatively huge drop of water. And it is a 

 common occurrence to see that animal live and move and strug- 

 gle until the water-drop has been absorbed so as to allow the 

 food-mass to come in actual contact with the digestive proto- 

 plasm. What becomes of that water ? Infusoria are voraci- 



