286 Scientific Intélligence. 
5. Fossil vertebra of Shark, (Trans. Roy. Soc., Edinb., xv, 648.)— 
The vertebrae of most cartilaginous fishes have been shown to have a bony 
nucleus or framework, and many do actually occur in the fossil state. 
6. General views on the Classification of Animals; by J. D. Dana, 
(Proceed. Acad. Nat. Sci. Philad., ii, p. 281, Oct. 1845.)—In Cuvier’s 
classification of animals, the division Radiata includes all invertebrated 
animals not comprised in either of the sub-kingdoms, Articulata and 
Mollusca. Consisting thus only of refuse species, and not limited by 
positive characters, as Owen states, we should not expect that the group 
could be a natural assemblage. No line of subdivision, however, has 
yet been made out, which has met with general favor; yet greater pre- 
animal kingdom, by appealing to the nerves, the seat of sensibility and 
sentiment, as a basis in classification ; and in this manner the subdivis- 
ions have been characterized as follows by Dr. Grant. 
I. The Vertebrata, having a brain and a spinal cord, constitute the 
Srint-Vertesrata. II, The Mollusca, having the nerves forming gen- 
erally a transverse series of ganglia disposed around the cesophagus, 
the Cycro-canetiata. III. The Articulata, having no proper brain, 
and the main cord which runs the length of the body, double, the 
Dirto-nevra. IV. The Radiata, having a radiate structure in the 
body, and the nervous ganglia arranged in a circle, CycLo-NEURA. 
An objection might be made to this system, on the ground of the 
apparent absence of nerves in some of the lower orders. But a real 
absence can hardly be concluded from our inability to distinguish them. 
Many of these animals show by their voluntary motions and sensibility 
that nervous influences traverse the body: moreover, nervous matter 
is secreted in lines. We can therefore only infer the indistinctness, 
and not the absence of nerves from our ineffectual efforts to trace them 
out; and we must consequently be guided by general structure, in de- 
termining the relations of groups, when the nerves fail of giving aid. 
The above arrangement fails, in some respects, of presenting @ clear 
idea of the system in nature, although highly philosophical in its gene- 
ral features. A study of the animal kingdom, as has been lately shown, 
brings to light lines or general systems of development branching up 
from the lowest Infusoria to the higher grades of life. It is not true 
that the forms among the lower grades are actually copied in any of the 
imperfectly developed young of the superior ; yet there is some gene- 
ral analogy, sufficient to indicate that the former commence on the 
same system of development with some of the latter, although carried 
essentially out of. the direct upward line by the peculiar vital forces of 
the species. The Rotifera are decidedly crustacean in type. Their 
stout mandibles are precisely those of the Cyclopacea in position, and 
cision has been given to our views of the affinities that.run through the - 
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