REVIEWS. 417 



The Cilio-flagellata are intermediate in characters between 

 the flagellate and ciliate Infusoria. Like the Flagellata, 

 they possess, as their chief organ of locomotion, a long 

 whiplash-like cilium or flagellum, in addition to which they 

 are provided, like the Ciliata, with ordinary small vibratile 

 cilia, usually restricted to an incomplete annular baud round 

 the body. 



The form of the body is always bilaterally asymmetrical ; 

 that is, there is a clear distinction between dorsal and ven- 

 tral aspects, anterior and posterior end's, and right and left 

 sides ; but the two latter never resemble one another per- 

 fectly, the body being divisible into two unequal and dis- 

 similar portions by a median vertical plane. The variations 

 in the form of the body are very great; it may be com- 

 pressed from before backwards, or from above downwards, or 

 from side to side, and may be produced into remarkable horn- 

 like processes, which are characteristic of particular genera. 



Except in three genera, the body is provided with an 

 exoskeleton, in the form of a membrane, which may be 

 either structureless or variously ornamented. On the ventral 

 aspect there is, in most genera, either a large aperture or a 

 longitudinal slit in the membrane, through which the pro- 

 toplasm comes into direct contact with the exterior. There 

 is also usually a transverse groove, through apertures in 

 which the cilia are protruded. 



But the point of chief interest in the skeleton is its 

 chemical composition. Bergh has succeeded in proving, by 

 numerous chemical tests applied to a large number of species, 

 that the membrane consists of cellulose, or at any rate of 

 some very similar carbo-hydrate. This, I believe, is the 

 first time that cellulose has been actually demonstrated in 

 the cell-wall of the Protozoa, the only case in which that 

 substance has hitherto been known in the animal kingdom 

 being that of the Tunicata. 



Equally important are the results of the investigation 

 of the contained protoplasm of these organisms. It is 

 usually divided into ectoplasm and entoplasm, the latter of 

 which is found to contain chlorophyll, diatomin (the yel- 

 lowish-brown colouring matter of diatoms), and starch. 

 Chlorophyll is already known to occur in many animals of 

 widely-separated groups, starch has hitherto been proved to 

 exist only in the green Turbellarians, and diatomin has never 

 before been known out of the vegetable kingdom. 



Professor Huxley says, speaking of the differences between 

 animals and plants,^ " The most characteristic morpho- 

 ' 'Anatomy of Invert, Animals/ p. 45. 



