neio Ivfiisoria from American Fresh Waters. 107 



tlie thin anterior right-liand membrane being at times thrust 

 into the oral fossa or arched above it like a protecting shield. 

 The enclosed superior vibratile tuft of cilia which, so far as I 

 have observed, never protrudes beyond the margin of the oral 

 fossa, is, when not in motion, usually pressed upward against 

 the roof of the cavity, and when the Infusorian is viewed in a 

 lateral position, or in vertical optic section, appears like tlie 

 thickened edge of a vibratile membrane ; it is only when the 

 animalcule is examined by focussing through the thickness of 

 the body from the dorsal surface, or when the creature fortu- 

 nately comes to rest with the ventral aspect towards the ob- 

 server, that the true character of the organ can be ascertained. 

 The cluster widens posteriorly by a separation of its constituent 

 cilia, as also does the lower and more nearly external frontal 

 tuft. The latter, however, seldom or never vibrates. Its 

 function appears to be to assist in imprisoning the food by 

 closing down over the cavity, or by entering the latter in 

 company with the undulating membrane. 



The setose hairs extending beyond the cuticular cilia are 

 about twice their length. They are evidently tactile in func- 

 tion, being used to inform the Infusorian of the approach of 

 food or of an enemy to be avoided. If the forme i-, the ani- 

 malcule immediately and most actively leaps upon it, seizing 

 and forcing it into the endoplasm so quickly that, although I 

 have repeatedly witnessed the act, I am ignorant of the pre- 

 cise method employed in the capture. If an approaching 

 free-swimming animalcule ever so slightly touches a setose 

 hair on any part of the surface, Histiohalaatiam at once leaps 

 upon it, frequently making a half-revolution on the transverse 

 axis, and seldom missing the object wished for. The undu- 

 lating membrane closes over the oral depression, often forcing 

 itself within the cavity ; the Infusorian makes a strong con- 

 tractile, somewhat convulsive effort, at once reminding the 

 observer of the similar movement by Floscidaria ornata when 

 food is passing onward towards the mastax, and the captive is 

 dashed through the oral aperture into the posterior part of the 

 boiy, whence it is gradually transferred to the anterior and 

 dorsal regions for digestion. The whole act is performed with 

 remarkable swiftness, the food being accompanied by an 

 unusually large bubble of water, as if the oral fossa had 

 poured its entire liquid contents into the endoplasm. This 

 habit probably accounts for the development of tlie multiple 

 contractile vesicles. The peculiar springing movements 

 described are, it is supposed, caused by the sudden action of 

 the setose hairs so abundant on the body. 



The entire oral apparatus is remarkably comnlex. I may 



