II. The Second division, Heliozoa, ' consists of the Rhizopods whose pseudopodia extend themselves as straight radiating rods, having little or no tendency to subdivide or ramif though they are still sufficiently soft and homogeneous (at least in t e lower types, to coalesce when they come into contact with each other. These have usually (probably always) a contractile vesicle as well as a nucleus; and the higher forms of them are characterized by the inclosure of peculiar yellow corpuscles (whose import is unknown) in the substance of their endosarc. By far the larger number Of this group also have Skeletons of Mineral matter, which are always siliceous; and these are sometimes perforated casings Of great regularity of form, as in the marine Poly c stina sometimes internal frameworks of marvellous symmetry, as in t e marine Radiolaria. These two groups, also, will be reserved for special notice (chap. XII.) the simple Heliozoa which are among the commonest inhabitants of fresh water, furnishing the best. Illustrations of the essential characters of the type. They seem for the most part to have but little locomotive power, capturing their prey by their extended pseudopodia.

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