418 REVIEWS. 



logical peculiarity of the plant is the investment of each of 

 its component cells by a sac, the walls of which contain 

 cellulose or some closely analogous compound ; and the 

 most characteristic physiological peculiarity of the plant is 

 its power of manufacturing protein from chemical com- 

 pounds of a less complex nature. The most characteristic 

 morphological peculiarity of the animal is the absence of 

 any such cellulose investment. The most characteristic 

 physiological peculiarity of the animal is its want of power 

 to manufacture protein out of simpler compounds.^' 



It will be seen that both these distinctions break down in 

 the case of the Cilio-flagellata ; their cell-wall is proved — 

 as Huxley suggested might be the case, in a note to the 

 passage just quoted — to be practically identical with that 

 of plants, and the presence of starch proves clearly that the 

 chlorophyll has the same function as that of plants, the 

 decomposition of the carbonic acid in the surrounding 

 medium. Bergh, indeed, believes that in many genera the 

 nutrition is entirely like that of a plant, and that no solid 

 nuriment is ever taken up ; and great weight must be 

 attached to an opinion founded on so many careful observa- 

 tions, though I must confess that the ventral aperture in 

 the test becomes somewhat inexplicable if it is not to be 

 looked upon as an ingestive area. Still, there can be no 

 doubt that if the Cilio-flagellata were an isolated group, 

 Bergh's researches would oblige us to consider many of 

 them as indubitable plants, and it is only comparative 

 morphology which forbids this view of their affinities. They 

 are so closely allied, on the one hand, to the Flagellata, 

 many of which possess the most undoubted animal charac- 

 teristics, and on the other, to the Ciiiata, which no one 

 would dream of considering as plants, that their systematic 

 position must remain unaltered, and they must simply be 

 taken as another and very striking instance of the impos- 

 sibility of draAving anything like a hard-and-fast line 

 between the animal and vegetable kingdoms. 



As to the systematic arrangement of the group, Bergh 

 divides it into two families, one of which — the Adinida — 

 contains a single new genus and species, Prorocentrum 

 ?mcans ; while the other — the Dinifera— contains three sub- 

 families and eleven genera. 



Prorocentrum, discoxeredhy Bergh, is interesting asforming 

 the nearest ally of the group to the Flagellata. It has an oval 

 compressed body, with both flagellum and cilia at the an- 

 terior end, and possesses neither transverse nor longitudinal 

 grooves. Its membrane consists of two valve-like moieties. 



