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Show 112 HYPOTHESIS OF THE DEVELOPMEN'l' OJ' change upon the embryo. It is not the different food \vhich effects a- metamorphosis. All that is done is n1ere .. ly to accelerate the period of the insect's perfection. By the arrangements made and the food given, the embryo becomes sooner fit for being ushered forth in its image or perfect state. Development may be said to be thus arrested at a particular stage--that early one at which the female sex is· complete. In the other circumstances, it is allowed to go on four days longer, and a stage is then reached between the two sexes, which in this species is designed to be the perfect condition of a large portion of the community. Four days more make it a perfect male. It is at the same time to be observed that there is, fron1 the period of oviposition, a destined distinction between the sexes of the young bees. The queen lays the whol(~ of the eggs which are designed to become workers, beforn she begins to lay those which become males. But proba .. oly the condition of her reproductive system governs the ~att~r of sex, for it is remarked that when her impregnation IS delayed beyond the twenty-eighth day of her enth·e existence, she lays only eggs ·.vhich become males. We have here, it will be admitted, a most remarkable illustration of the principle of development, although in an operation limited to the production of sex only. Let it not be said that the phenomena c.oucerned in the generation of bees may b~ very different frorn those concerned in the reproduction of the higher animals. There is a unity throughout nature which makes the one case an instructive reflection of the other. We shall now see an instance of development operating within the production of what approaches to the character of variety of species. It is f.ully established that a human family, tribe, or nation, is liable in the course of generations, to be either advanced from a mean form to a higher on~, or degraded from a higher to a lower, by the influence of the physical conditions in which it lives. The coarse features, ar.d other structural peculiarities o1 the negro race, only continue while these people livCJ amidst the circumstances usually associated with barbarism. In a more temperate clime, and higher social state, the face and figure become greatly refined. The few African nations which possess any civilization also exhibit forms approaching the European; and when the same people in the United States of America have enjoyed a /J THE VEGETABLE AND ANIMAL X INGDOMS. 113 :11ithin-door life for several generations they assimilate to the whites amongst whom they live. On the other hand, there are authentic instances of a people originally well-formed and good-looking, being brought., by imper.. ect diet and a variety of physical hardsltips, to a meaner form. It is remarkable, that prominence of the jaws, n recession and diminution of the cranium, and an elongation and atenuation of the limbs, are peculiarities always produced by these miserable conditions fot· they indicate an unequivocal retrogression towards the type of the lower animals. Thus we see nature alike willing to go back and to go forward. Both effects are simply the result of the operation of the law of development in the generative system. Give good conditions, it advances; bad ones, it recedes. Now, perhaps, it is only because there is no longer a possibility, in the higher types of being, of giving sufficiently favorable conditwns to carry on species to species, that we see the operation of the law so far limited. Let us trace this law also in the production of certain classes of monstrosities. A human fcetus is often left with one of the most important parts of its frame imperfectly developed: the heart, for instance, goes no farther than the three-chambered form, so that it is the heart of a reptile. There are even instances of this organ being left in the two-chambered or fish-form. Such defects are theresult of nothing more than a failure of the power of development in the system of the mother, occasioned by weak health or misery. Here we have apparently a realization of the converse of those conditions which carry on spe .. cies to species, so far, at least, as one organ is concerned . Seeing a complete specific retrogression in this one point, how easy it is to imagine an access of favorable conditions sufficient to reverse the phenomenon, and make a fish mother develop a reptile heart, or a reptile mother de .. vdop a mammal one. It is no great boldness to surmise that a super-adequacy in the measure of this under-adequacy, (and the one thing seems as natural an occurrence as the other) would suffice in a goose to give its progeny the body of a rat, and produce the ornithorynchus, or might give the progeny of an ornithorynchus the mouth and feet of a true rodent, and thus complete at two stages the passage from the aves to the mammalia. Perhaps even the transition from species to specias does |