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account, themselves constitute a new style; and the Provinces Molluscoida and Annuloida of Huxley, which, as their names indeed import, are in the main merely simple forms of Mollusca and Articulata.

6. DIVISION OF PROVINCES INTO CLASSES.

Having formed our Primary divisions or Provinces on the ground of type or plan, we must, in dividing these into classes, have regard either to subordinate details of plan, or to some other ground. In point of fact, naturalists seem to have tacitly agreed to form classes, on what Agassiz terms the "“ manner in which the plan of their respective great types is executed, and the means employed in their execution." In other words, they have in forming classes adopted, perhaps unconsciously, a functional system, similar to that employed by Oken in forming his primary groups. They have taken the relative development of the four great functional systems of the animal,-the sensative, the locomotive, the digestive, and the reproductive. This is very

manifest in the ordinary and certainly very natural sub-division of the vertebrates into the four classes of Mammals, Birds, Reptiles,* and Fishes. The Mammals are the nerve or sensuous animals, representing the highest development of sensation and intelligence. The Birds are eminently the locomotive class. The Reptiles represent merely the alimentary or vegetative life. The Fishes are the eminently reproductive or embryonic class.

If this is a natural division of vertebrates into classes, and if the other three Provinces are of equivalent value, then there should be but four classes in each, one corresponding to each of the great functional systems. We may name the first of these the nervous class; the second, the motive class; the third the nutritive class; the fourth, the reproductive or embryonic class. Let us then endeavour, as a test of the truth of this system, to make such an arrangement of the classes of the animal kingdom.

• The Amphibia, as Dana well argues on the principle of cephalisation, are clearly Reptiles, because we arrange animals in their mature and not in their embryonic condition, and because the points of reproduction in which Amphibia differ from ordinary reptiles, have relation to an aquatic habitat, and are ordinal or rank characters merely.

TABLE OF CLASSES OF ANIMALS.

Provinces or
Branches.

Vertebrata. Articulata.

Mollusca.

Radiata.

1. Nervous class. Mammalia.. Arachnida. Cephalopoda.....| Echinoder2. Motive class... Aves... .. . . Insecta.... Gasteropoda (in

[mata.

cluding Pieropoda)

Acalephe.
Anthozoa.

3. Nutritive class. Reptilia.... Crustacea... Lamellibranchi

[ata.

4. Embryonic or Pisces..... Annulata.. Molluscoida (in

Reproductive class.

......

cluding Tunica-
ta, Brachiopoda,
Bryozoa,... Protozoa.

All of the above groups are recognized by common consent as classes, except a few which have been already incidentally adverted to, and to which it is not necessary again to refer here.*

It will be observed that the order in descending the columns is that of affinity; that in reading across the columns is the order of analogy. The affinities no naturalist will seriously doubt. The analogies may be less familiar. In examining them, it will be seen that the first class in each province includes animals remarkable for condensation of the head and body, where the former exists; for high nervous energy, sensation, and intelligence; for prehensile apparatus, and for absence or simplicity of metamorphosis. The classes in the second line are characterized by the greatest locomotive powers in their respective provinces; those in the third line by the development of the nutritive apparatus and of vegetative growth; those in the fourth line by embryonic characters when mature, and by abundant reproductive energy. It will be observed also as a necessary consequence of the system we have pursued, that each of our classes includes animals of very various rank or grade. Indeed, most of them have at their bases forms so simple or imperfect that it is almost impossible to include them in the class-characters. This is no objection to our arrangement, but a proof of its correctness; for we have now arrived at the point where we must form Orders based solely on

* The rank given to the Arachnida will be disputed by some naturalists; but a consideration of the structures of these animals will show that their relations to the insects and the crustacea are similar to those of the mammals to the birds and the reptiles; and that it is no more reasonable to say that the arachnidans are nearer to the crustaceans than to the insects, on the ground of general structure, than it would be to do the same in the case of the mammals and the reptiles as compared with the birds.

this consideration of rank. Of these humbler members of our classes we may mention the Marsupials and the Monotremes among the mammals, the Amphibia among the reptiles, the Mites among the arachnidans, the Myriapods among the insects, the Entozoa among the worms. Indeed it is quite possible on this ground to

This is

divide each of our classes into two or more Sub-classes. sometimes convenient for the sake of more accurate definition; but it is not necessary, since the division into orders sufficiently expresses these grades of complexity or elevation.

7. DIVISION OF CLASSES INTO ORDERS AND FAMILIES. Orders, as already stated, are based principally on rank or grade, to be ascertained by relative complexity or by the development of the higher nature of the animal. The last section, however, obliges us to take this with some limitation; for since we have four descriptions or sorts of classes, each of these must have the grade within it ascertained on special grounds. For example, the orders of birds, insects, gasteropods, and acalephæ, should be ascertained chiefly by reference to the locomotive organs, as being the system of organs most eminently represented in the class. If we glance for a moment at the systems which have been proposed, we shall see that this view has unconsciously commended itself to naturalists. The orders of insects, for example, are very plainly based on such characters, being founded mainly on the wings. This is nearly equally manifest in the ordinarily received orders of birds. It appears in the division into Pteropods, Heteropods, and Gasteropods proper among the Gasteropoda. It is also seen in the orders Ctenophora, Discophora, Siphonophora, among Acalephæ. It would be easy to show by a detailed review of the orders in the animal kingdom, that, in so far as they have been distinctly defined, they have in most cases been framed with a reference to the prevailing characteristics of the class; and also with the idea of grade or rank as a leading ground of arrangement. As previously observed, also, it is in the construction of orders, and in ascertaining rank in other divisions, that embryology and the doctrine of cephalisation are chiefly useful. For the present, however, we must leave this subject until we shall have an opportunity to enter into descriptive zoology.

In Botany, orders and families are identical. In Zoology we use the term Family for a group inferior to an order, and equivalent to the sub-order or tribe in botany. The family con

sists of an assemblage of genera resembling each other in general aspect. Most large orders are readily divisible into such assemblages, which, though in themselves somewhat vague, have the advantage of being formed on grounds which, being conspicuous and obvious at first sight, much aid the naturalist in the preliminary parts of his work. For example, among the carnivorous

mammalia such groups as the Mustelida or weasels, the Cunida or dogs, the Felidae or cats, are so obvious that any member of one of these groups can be referred to that to which it belongs almost at first sight. Still I do not regard families as necessary divisions of the order. Some small orders may not admit of division into families; and even where such division is admissible, the genera may be studied as members of the order, without being grouped in families, though this grouping is often very useful and convenient.

It is important to observe, before leaving this part of the subject, that, in consequence of the great multiplication of species in some groups, and the close scrutiny of their structures, it is the tendency of specialists to form many small genera. This leads to the construction of numerous families, many of which would more properly remain as genera. A still worse consequence is, that, instead of forming sub-orders and sub-classes, such specialists often call sub-orders or even families orders, and raise sub-classes or orders to the rank of nominal classes, thus introducing a confusion which leads the student to suppose that these terms have no definite meaning. I would further observe here, that I do not so much insist on the use of one name for a group rather than another, as on the constant use of each term for groups truly equivalent in the system.

It may be necessary here to state that the formation of orders on the ground of rank, and of families on the ground of general aspect, does not exclude the ideas of rank and general aspect from the province or class. On the contrary, as a secondary ground, general aspect is a good character in the province and class, and a gradation of rank can be perceived in provinces and classes. In the provinces, the Vertebrata stand highest, and the Radiata lowest, the Articulata and the Mollusca being nearly equal, and their lower members not so high as the highest Radiata; so that they would stand in a diagram thus:

[blocks in formation]

So among classes, the nerve class in each province is the highest. and the embryonic class the lowest, and the other two intermediate; but the idea of rank is not here the primary one, as it is in forming the orders. It is also true that from the province downward the idea of type or plan is constantly before us.

We have now in descending from provinces reached the genera and species, with the consideration of which we commenced; and if the preceding views have been understood, we shall be prepared to commence the study of Descriptive Zoology, or to enter upon the details which fill up the outline which has been sketched. In doing this we must take specimens of known species and study them in their structural and physiological peculiarities, and in their relations to the other species congeneric and co-ordinate with them.

ON THE OCCURRENCE OF PIERIS RAPÆ IN CANADA. By G. J. BOWLES, Sec. Ent. Soc. of Canada, Quebec Branch.

During the summer of 1863-my first collecting season-I captured in the vicinity of Quebec numerous specimens of a but terfly of which no description could be found in any work on American entomology. Mr. Couper, to whom I applied for assistance, was equally at a loss to determine the species, considering it, as I did, to be indigenous to Canada. In order to solve the problem, however, he forwarded some specimens of the imago to Mr. William Saunders, of London, C. W., who pronounced them to be identical with Pieris rape, the small white butterfly of England, one of the most common and injurious lepidopterous insects of that country. In the meantime I had enclosed a drawing of the butterfly, together with the wings, to Mr. S. H. Scudder, of Boston, Mass., from whom I received a reply, stating that after comparing the drawing and wings with specimens of P. rapa in the Museum of Comparative Zoology at Cambridge, he saw no reason to consider them distinct: at the same time he desired further investigation to be made respecting the larva and pupa states of the insect. This investigation has been successfully carried out, and places beyond doubt the identity of the butterfly with the English P. rapa, thus establishing another instance of the transportation of a lepidopterous insect across a wide expanse of ocean, and its naturalization in

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