21 



The second group, the Perforata, are of a " hyaline or vitreous type," and 

 are perforated in nearly every direction by minute holes {Foramina), through 

 which the animal passes long filaments, the so-called Pseudopodia. The 

 texture of these shells is firmer than those of the first group, approaching 

 inferior forms of dentine. 



The third group is the Arenaceous, the test being partially or wholly 

 formed from sand, varied by the introduction of sponge spicules, or 

 smaller foraminiferous shells, fixed by an animal cement insoluble in 

 •caustic potash, suggesting a composition analogous to the chitinous integu- 

 ments of insects. The tests of this division contain 60 per cent, of silica, 

 and the foreign bodies are incorporated by a layer containing Ferric Oxide 

 and Carbonate of Lime, in variable proportions, the oxide being usually in 

 excess. 



These three variations are not confined to particular forms of the shells, 

 for similar contours present themselves in all of them. 



In the first division, Imperforata, there are one or two openings, from 

 ■which the animal protrudes and retracts on the approach of danger, and 

 the animal being within the test, the test is an exoskeleton; but in the 

 Perforata, the substance of the shell is traversed by delicate canals 

 (Foramina), which allow the extrusion of the body of the animal in 

 numerous protoplasmic filaments coalescing covering, and enclosing the 

 shell or test, thus having the nature of an endo skeleton. Curious to find the 

 two great types of the animal kingdom indicated in such lowly forms. 



The simplest adult form is a cell-like shell, " Squamalia," or a discoidal 

 spiral lube, " Cornuspira." The spherical " Orbulina " and flask-shaped 

 " Lagena " are also simple forms, and possessing one chamber are called 

 ■" Monothalamous," and are the embryonic starting points of all the types. 

 The hard casing covering the animal, once formed, cannot be enlarged to 

 accommodate the growing requirements. This can only be accomplished 

 by additional chambers added to the original one, and thus the Monothala- 

 mous forms pass into the Polythalamous. When, with additional chambers, 

 a lineal series results, they are nodosaria ; if curved, cornuspira ; if in 

 segments, rotalia ; or wound round a long axis, miliola. If they are 

 irregularly aggregated they are glohigerina, or the chambers may overlap 

 as in nummulites. These calcareous and arenaceous shells are similar to 

 the skeletons of sponges and corals. 



It is usual to assign to Haeckel the establishment of a new kingdom, at 

 the base of the Zoological scheme. He certainly, about 20 years ago, 

 proposed his hypothesis, that there existed a third kingdom in addition to 

 the animal and vegetable — a borderland, which he named " Protista" ; but as 

 early as 1859, Owen introduced a kingdom, " Protozoa," to occupy the 

 lowest position, and was immediately followed by John Hogg, with his 

 " Protoctista," which included both "Protozoa" and " Protophyta." 



Haeckel describes the lowest division of his " Protista," the " Monera," 

 as " not only the simplest, but the simplest conceivable organism, originated 

 by spontaneous generation at the beginning of life upon the earth. They 



