. Cassell's natural history. Animals; Animal behavior. ^^»'*-*--^^ -^ (i; and a flagellum also. The fact that tlie Tentaculifera are totally unlike the other Infusoria in their adult age is very remarkable; but it is evident that before they attain maturity they resemble the Ciliata. New structures are thus, by evolution, given to the Tentaculifera, and they have considerable affinities with the Rhizopoda. Their adult form fe in advance of the ciliate young one, and the order Tentaculifera must stand at the head of the Infusoria. Next conie the Ciliata, then the Cilio-flagellata, and, finally
. Cassell's natural history. Animals; Animal behavior. ^^»'*-*--^^ -^ (i; and a flagellum also. The fact that tlie Tentaculifera are totally unlike the other Infusoria in their adult age is very remarkable; but it is evident that before they attain maturity they resemble the Ciliata. New structures are thus, by evolution, given to the Tentaculifera, and they have considerable affinities with the Rhizopoda. Their adult form fe in advance of the ciliate young one, and the order Tentaculifera must stand at the head of the Infusoria. Next conie the Ciliata, then the Cilio-flagellata, and, finally, the Flagellata. The Infusoria are uni-cellular, and this is true where there are two or more individuals in close contact, or where a common stem supports the bodies of others, which may be numerous. For in these instances4|Subdivision of the parent has pro- duced the independent creatures. In the Tenta- culifera, however, the most highly-organised amongst the Infusoria, in the .species called Dendrosoma radians (Fig. 6), there is a root com- mon to many trunks which give origin to branchlets terminating in a bundle of tentacles with suckers. This arrangement can hardly be called uni-cellu- lar ; there is, however, no actual cell division, and indeed the ordinary idea of the single cell is hardly applicable to this and many other Infusoria. The simplest Infusoria belonging to the Flagel- lata, which have no special spot for the ingestion of food,* have no distinct environing membrane over their soft finely granular protoplasm, and they ^ ^ '» â = 'J \ It A ^'^ ^ "^ "'" "" can assume various shapes for a while. Others belonging to the same group have the outside of the body slightly more solid than the rest. In the Ciliata the presence of an outer membrane is evident, and it is possible to distinguish, on some of them, four layers around the soft semi-fluid central endoplasm. On. the outside is a perfectly transparent structureless membrane, and
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