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Show 84 ON CLASSIFICATION. . . 1 d for the n1ost part, with long and of co~tract~le vesiC es, tnr~n into one another and. become pseudopodia, whiCh common Y reticulated. h T7 l ssn'collfJ3 provided with structureless 3rd That of t e '~a a (I ' · . . ll 1 . lements and sarcode, and surrounded cysts containing ce u ar e · h' h 1 by a layer of sarco d e, gi· ving off pseudopo.d ia, w IC common y 1 l stand out h.k e rays, b u t m ay and do run Into one anot 1er, anc so form networks. Fig. 38. Fig. 38.-Splum·ozoum ovodimare (after Haeckel), one of the Tlwlassicollre. While a fourth type of structure is probab~y .furnished by those anomalous creatures, the AcinetfJ3, the rachating process~s of which serve as suctorial tubes down which the juices of thmr prey are conveyed. That the Rhizopoda are divisible into at least three grm~ps, corresponding to the three first-mentioned types of organization seems to me unquestionable; but it is another matter, and one' on which I offer no opinion, what should be the exact limits of these group~, and what denominations we ough~ t~ employ for them. And it must be recollected that, so long a naturalists are unacquainted with the sexual method of repro- 'l'HE EIGII'l' PHIMAHY GROUPS OF ANIMALS. 85 duction of these animals, they are, to a certain extent, working in the dark. In conclusion, I may sum up the results of this lecture by stating that, in the present state of our knowledge, the whole Animal IGngdo1n is divisible into eight primary categories or groups, no two of which are susceptible, in the present state of knowledge, of being defined by characters which shall be at once common and diagnostic. 'rhese groups are the- MoLLuscA. MoLLuscornA. CmLENTERATA. V ER'l'EBRATA. Pno'rozoA. ANNULOSA. ANNULOIDA; INFUSORIA. I leave aside altogether the question of the equivalency of these groups ; and, as I have already stated, I entertain some doubts regarding the permanency of one--the Inf~tsoria-as a distinct primary division. Nor, in view of the many analogies between the Mollusca and the Molluscoida, the Annulosa and the Annu.Zoida, do I think it very improbable that, hereafter, some common and distinctive characteTs may possibly be discovered which shall unite these pairs respectively. But the discoveries which shall effect this simplification have not yet ueen 1nade, and our classification should express not anticipations, but faets. I have not thought it necessary or expedient, thus far, to enter into any criticism of the views of other naturalists, or to point out in what respect I have departed from my own earlier opinions. But Cuvier's system of classification has taken such deep root, and is so widely used, that I feel bound, in conclusion, to point out how far the present attempt to express in a condensed form the general results of comparative anat01ny departs from that embodied in the opening pages of the "Regne Animal." 'rhe departure is very nearly in the ratio of the progress of knowledge since Cu vier's time. 'rhe limits of the highest |
