to grow stronger as it was derived by inheritance from a greater number of generations, and thus the nest of the species that had so aristocratic an heir-loom, would become better provided with workers, and except in this matter of slave-making, less and less inclined to work. Formica rufescens furnishes us with this precise parallel to a degenerate community of men.! "This ant is absolutely dependent on its slaves; without their aid, the species would certainly become extinct in a single year. The males and fertile females do no work. The workers or sterile females, though most energetic and courageous in capturing slaves, do no other work. They are incapable of making their own nests, or of feeding their own larvæ. When the old nest is found inconvenient, and they have to migrate, it is the slaves which determine the migration, and actually carry their masters in their jaws. So utterly helpless are the masters, that when Huber shut up thirty of them without a slave, but with plenty of the food which they like best, and with their larvæ and pupa to stimulate them to work, they did nothing; they could not even feed themselves, and many perished of hunger. Huber then introduced a single slave (F. fusca), and she instantly set to work, fed and saved the survivors; made some cells and tended the larvæ, and put all to rights."p. 219. We do not say, nor does Mr. Darwin say, that formica rufescens is the descendant of sanguinea; but it does not seem improbable that rufescens was once as active as sanguinea is now, or that the time may come when sanguinea, that now on a migration carries its slaves. in its jaws, may condescend to be carried by them. It will be seen, therefore, that we are willing so far to assent to Mr. Darwin's reasoning as to say that an instinct may have received grave modifications, or even have entirely originated by degrees, and as exemplifications of the rule which our author pithily lays down (p. 244.) in the words," multiply, vary, let the strongest live and the weakest die." We do not see how the intrinsic distinction between instinct and inherited habit can be maintained by Mr. Darwin and his friends. Habits would be perpetuated in consequence of the advantages accruing from them, and so become instincts. A habit utterly valueless to the individual, as pointing in the dog, might be inherited in a state of nature, but unless it were advantageous it would soon die out. But when the habit greatly promoted the good of the species, those that had it most strongly would flourish the most, and would verify the rule, "let the strongest live." The quails that crossed the Mediterranean would have had such an advantage over other quails that the habit of migration would come to be hereditary and instinctive. Passing on to another portion of the subject which Mr. Darwin has felt to contain a very serious difficulty on his theory, we hope that in giving in our adherence to his position we are influenced by the validity of his argument, and are not led away by the attractive candour with which he admits the weight of the difficulties he has to encounter. He carefully examines into the case of neuter or unfertile insects, which are of course unable to perpetuate their own peculiarities; and he comes to the conclusion that even in the striking instances in which the working ants differ from one another so much as to be divided into two or even three castes, the principles of variation that he has laid down will be found to apply. In other words, those families where nature first instituted "the division of labour," by confining the operation of certain inmates of the hive or nests to active work only, leaving to others the propagation of the species, would be the most flourishing communities, and thus would excel and outlast their competitors. The idea is not more difficult than that nature should confine the operation of an organ, which originally fulfilled two functions, for the future to the discharge of one function only. Thus fertile parents would produce fertile and sterile offspring, and they would transmit to their fertile progeny the tendency to produce a family divided in qualities as they themselves have done. Nothing is more probable than that such unproductive workers would be very variable; for any variation that improved their working power would be advantageous, and would be likely thus to be preserved: although it is somewhat startling to meet with such diversity as in the workers of the driver ant of West Africa, in which "the difference is the same as if we were to see a set of workmen building a house, of whom many were five feet four inches high and many sixteen feet high," while, moreover, the larger workmen had heads four instead of three times as big as those of the smaller men, and jaws nearly five times as big." We are not surprised to learn (p. 241) that "though the workers can be grouped into castes of different sizes, yet they graduate insensibly into each other." In fact no one who is convinced by Mr. Darwin's previous proofs and reasoning, will be long delayed by the curious case of sterile insects. For our part we must say that we see no improbability in all the various species of ants on the face of the earth having descended from a common stock, or in all the species of bees and wasps being in the same relationship to one another, we can readily join our author in the retrospect which he thus words: For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic horse, whether or not it be descended from one or more wild stocks of the ass, the hemionus, quagga, and zebra. (p. 167.) 66 Leaving untouched many topics most ably handled by Mr. Darwin, as the analogy of variations in allied species, and the prevalence of variation in dominant species, we give one extract from his observations on correlation of growth, and that on account of the singularity of the instances adduced. "What can be more singular than the relation between blue eyes and deafness in cats, and the tortoise-shell colour with the female sex; the feathered feet and skin between the outer toes in pigeons, and the presence of more or less down on the young birds when first hatched, with the future colour of their plumage; or, again, the relation between the hair and teeth in the naked Turkish dog, though here probably homology comes into play? With respect to this latter case of correlation, I think it can hardly be accidental, that if we pick out the two orders of mammalia which are most abnormal in their dermal covering, viz. Cetacea (whales) and Edentata (armadilloes, scaly ant-eaters, &c.), that these are likewise the most abnormal in their teeth."-p. 144. Under the term "correlation of growth," Mr. Darwin shows that variations, which have no evident utility, and which thus would not be preserved by the process already so often described to which he gives the name of natural selection, may be due to some unknown laws of relationship between the various parts of the organization. But we must confess that we do not see how the existence of useless members of a community, like the drones in a hive, square with Mr. Darwin's theory of selection by the pressure of severe competition. Surely if the competition amongst bees were very great, the hive that had the fewest drones would have the most honey for its working bees, and would thus in the end prevail. If natural selection has been so powerfully at work that to save a waste of time and wax, it has taught the bee to make its wonderful comb, (p. 233.) and to destroy its drones, how comes it when one single male is all that is needed to pair with the queen, and that, as Huber thinks, but once in two years? how comes it that natural selection has not diminished the number of the drones? Diminished we say, for if there be any truth in this modification of species, as we are willing to believe, then is the multiplicity of drones an inheritance from the day when the working bees were also fruitful and required a mate. It is well to remark that there are cases in which nature herself, in her attempt to fulfil the law" increase and multiply," devotes sundry and sometimes many members of the family to the celibate life! 66 66 It will be at once deduced from Mr. Darwin's theory, that he regards the difference between species and varieties as arbitrary. "A well-marked variety may be justly called an incipient species." (p. 52). Species are only strongly marked and permanent varieties." (p. 56). “ Varieties tend to become converted into new and distinct species." (p. 59.) Nor do we know of any difficulty, save only one, which stands in the way of the immediate acceptance by naturalists of this assertion. That one difficulty, and it is a very grave one, is the sterility of species, and the fertility of varieties, when intercrossed. Beyond a doubt if this difficulty holds good, the whole of Mr. Darwin's web has been spun in vain. It would establish an intrinsic difference between a species and a variety, which would be fatal to the theory. Our author has shown brave fight against this opponent, and we think with marked success. He has first distinguished the sterility of the first cross between two different species from that of the hybrid, and he explains both one and the other by the very principle which he lays down at starting, respecting variation; and it must be confessed that it speaks favourably for a theory when it is brought as the key to unlock the very objection against itself. The conditions of life affect the entire organism, and especially its reproductiveness. Thus it produces variations, and thus sterility. Domestication gives us striking instances of both. Varying conditions of life have affected our horses, dogs, pigeons, and fowls, and their offspring have widely varied from the parent stock. Our Zoological Gardens furnish us with numberless animals that are perfectly healthy in confinement, but yet will not breed. It was for this reason that we said that we looked forward to the publication of the catalogues of facts affecting the reproductive system which Mr. Darwin promises us, as so valuable a help towards understanding on what success depends in the attempt to acclimatize and domesticate fresh species. The illustration he gives is almost a proof. As with ourselves, slight changes in the conditions of life, say of climate or occupation, are favourable, and violent changes are detrimental: so in animal and vegetable life, crossing with an individual slightly varying, is beneficial, while great variations constitute a bar. If there were thus an essential difference between species and varieties, there ought to be no produce at all in the case of a cross, and the production of a hybrid should be impossible. : "The canary-bird has been crossed with nine other finches, but as not one of these nine species breeds freely in confinement, we have no right to expect that the first crosses between them and the canary, or that their hybrids should be perfectly fertile." (p. 252). The circumstances are most unfavourable. If in If in a state of nature a mule were to be produced, it would then be a much fairer test; but this cannot be, for as, in nature, the principle of inheritance, of like producing its like, is a general law, so is also the cognate one, of like pairing with like. Further, our ideas of the sterility of different species when crossed, are derived in the main, from naturalists who have assumed it as a first principle, and have accepted it as a test to determine what differences were specific. Even thus, however, it does not hold good. To pass over the many instances of various species that produce mules, the few ascertained fertile hybrid animals, and the far more numerous fertile hybrid plants, there are cases of plants which can be far more easily fertilised by the pollen of another and distinct species, than by their own pollen." (p. 250). "A multitude of cases could be given of very closely allied species which will not unite, or only with extreme difficulty; and on the other hand, of very 66 |