SI 



r.KNKRATIONS, ALTERNATION OF. 



< I i:\KRATIONS, ALTERNATION OF. 



whiUt in others thry remain free tad active (the ' nurse* ' and ' parent 

 nurse*' of Oenmria rpkemrra and C. tcJtinata), but retain during their 

 whole life a form which, at most, resembles the larva) of the more 

 perfect generation. In thi way an advance in a certain direction 

 may indisputably be observed. At flrtt all the generation! constitute 

 a unity, not merely as regards the interior, but also with respect to 

 the exterior : they form a stationary colony ; after which the genera- 

 tions an detached more and more from each other, and become at the 

 same time more free ; and, finally, all the individunls constituting the 



station are_ separate from each other, and acquire the power of 

 locomotion. In this latter stage, or that of freedom and perfec- 



i, we found the development of animals which are certainly no 

 longer attached to inanimate objects at the bottom of the sen, but live 

 buried in other animal organisms, and belong not to the sea but to 

 fresh water. In a still higher and more free stage than this we observe 

 the development of animals which do not belong to the water, but to 

 the air, as in that which occurs in the Aphidet. The propagation of 

 thsto creatures through a series of generations has been already long 

 known. In the spring, for instance, a generation is produced from 

 the ova, which grows and is metamorphosed, and without previous 

 fertilisation gives birth to a new generation, and this again to a third, 

 and so on, for ten or twelve weeks ; so that in certain species even as 

 many as nine such preliminary generations will have been observed ; 

 but at last there always occurs a generation consisting of males and 

 females, the former of which, after their metamorphosis, are usually 

 winged ; fertilisation and the depositing of eggs takes place, and the 

 long series of generations recommences in the next year, and in the 

 same order. All the individuals are free, and enjoy the power of free 

 locomotion, and undergo a metamorphosis. Here, however, we have 

 before us aerial animals, and which are no longer parasites inhabiting 

 other organisms ; at most they are only externally parasitic, and on 

 plant* alone ; the phenomena of this mode of development are no 

 longer exhibited by i'ntaoa, but by Epiphyta. Nevertheless, the 

 course of development is in itself similar ; but in the external, more 

 free, and nobler form in which it is now exhibited, the endeavour to 

 attain something higher is manifest. Each link or generation certainly 

 brings its offspring nearer to the perfection aimed at; but this 

 approachment towards perfection is effected only by means of the 

 ' nursing ' by special animals, and is committed to the still and quiet 

 activity of an organ, without the nursing animals themselves being 

 conscious of it ; it is a function merely, and not an expression of the 

 will. In all parts of the animal kingdom we see instances of the 

 still, quiet, and unconscious activity of the animal being developed 

 into voluntary actions, which are undertaken by it from an internal, 

 obscure, and irresistible impulse (or artificial impulse), as is the case 

 in this instance. The development and mode of feeding or nourishing 

 the young, exhibited in its course, of Bees, Wasps, Ants, and Termita, 

 affords a direct example of the mode in which the care of the young 

 is provided for, by the voluntary action of numerous individuals 

 devoted to that object. Those of the young which are to be developed 

 into the more perfect, fertile individunls are not protected in the 

 body of the foster-parents, nor is their nourishment secreted by one 

 of the organs ; both protection and food are afforded them by means 

 which are brought about by the conscious activity of the ' feeders.' 

 The Wasp, for instance, or the Wild Humble-Bee, which has been 

 impregnated in the autumn, and has afterwards sought a shelter to 

 protect iUelf against the cold of winter, prepares a solitary habitation 

 in which it builds cells and deposits its eggs. From the eggs proceed 

 larvae, but the insects into which these larva- are metamorphosed, are 

 not fertile ; they are barren, and all their faculties are directed to the 

 assisting of the parent animal in the better nourishing of the future 

 brood, to which end some of their external organs are transformed, 

 and to the erection of a better habitation and cells, into which they 

 convey the eggs of the female, and the food of the larvae to be developed 

 from them. Other cells, which contain a better sort of food, are 

 erected for a later and less numerous progeny of eggs ; and again in 

 others, which are more roomy and provided with the best kind of 

 food, but of which there are only a few, is the last brood of the female 

 deposited. From the first kind of cells proceed the barren individuals, 

 from the second the males, and from the third the females ; after 

 undergoing a metamorphosis, the males and females fly away, impreg- 

 nation take* place, and the males die ; the females however return, 

 and the whole multitude of barren individuals, which at the same 

 time perform the duty of feeding the young, build cells for their 

 various progeny of eggs, and nourish the three forms of larva; which 

 procssd from them. In this way the inhabitant* of the colony become 

 very numerous ; nevertheless they all die off in the winter : the fertile 

 females alone remain alive, and propagate the species the year follow- 

 ing, under the same development of alternating broods, the earlier of 

 which is always by far the most numerous, and assists in the develop- 

 ment of the latter. In the colonies of Bees, Ants, and Termita, the 

 same thing occurs ; the many thousand individuals which constitute 

 one of these colonies are principally ' feeders,' or individuals which 

 have oritrinated in the precedent divisions of the eggs of the females, 

 and in these is exhibited, even with greater precision, a more marked 

 division of labour in the feeding of the progeny ; so that, out of the 

 varioiK precedent divisions, individual* apparently arise which assist 

 iu the iUvi:! i]uiiriit uf the more perfect progeny iu various ways. 



Thus there 'are in a hive of bees, individuals which are employed 

 almost wholly in the feeding of the larva; (foragers), whilst others do 

 scarcely anything else than collect wax and build cells (workers). In 

 ant-hills, one set of the feeders is constantly employed in conveying 

 the larva from one place to another, according as they require a 

 greater or less degree of warmth, Ac., whiUt others are engaged in 

 building the passages or earth-cells, and in making excavations around 

 the habitation. Among the Termita also we are acquainted with 

 several forms of ' feeders,' constituting particular tribe* or classes ; 

 the description of labour, however, which each of these classes par- 

 forms, is unknown. It is known, however, that a form with a large 

 head and strong jaws is always posted at the entrance of the artificially 

 constructed dwelling, and keeps guard there as soon as any disturbance 

 is remarked, and thus constitutes the safeguard not only of the young 

 but of the whole community. 



" Now in the cases in which the more perfect development of the 

 progeny is promoted, either by means of ' nurses' or of 'feeders' (under 

 which latter term we understand special individuals devoted to the 

 actual care or nourishing of the young, which office they fulfil by a 

 conscious activity), we see that nature always has in view the produc- 

 tion of a multitude of individuals to whose life or care is then com- 

 mitted the perfecting of a later generation or progeny, consisting of 

 less numerous individuals. This previous or preparatory multitude 

 seems to consist invariably of females, the males being apparently 

 excluded from any participation in the office, on whicti account the 

 males of all the animals among which the system of 'nursing' or of 

 ' feeding ' obtains, constitute a very subordinate number. That the 

 ' nursing ' should be committed to females alone appears to us very 

 natural, since we are acquainted with on organ in them whose natural 

 function would be to perform that office. The generative organs are, 

 indeed, in perfect (female) individuals divided, as it were, into two 

 parts of very distinct natures ; the ovarium for the preparation of the 

 germ and the production of the egg, and the oviduct and uterus, in 

 which the ova are, as it were, incubated, and the germ and embryo 

 sufficiently developed to allow of its being born. Now, it is actually 

 the case that no true ovary has been discovered in the ' nursing ' 

 generations ; on the contrary, the germs, as soon as they are percep- 

 tible, are situated in organs which must be regarded as oviducts and 

 uteri, as, for instance, in the most perfect ' nurses' we are acquainted 

 with, the Aphidu. In the ' nurses' of the trematode larva, the CVr- 

 taria echinata, I have remarked that the germs in their earliest 

 condition are collected into an organ at the root of the tail, which 

 may probably be regarded as a uterus, and that they appear to distend 

 this organ gradually to the size of the whole body. The accurate 

 anatomical researches of Professor Eschricht on the Salpa also show 

 in the most precise way that the associated brood of the Salpae does 

 not originate from ova, but that, as germs which are arranged iu a 

 definite manner between the walls of a hollow organ, it is contained 

 in what can in no case be an ovary, and which the author has termed 

 a ' germ-tube.' This organ lies in a cavity which may probably be 

 considered very nearly a uterus, which is however always, as it were, 

 a secondary receptacle for the germs ; but in the present instance it 

 cannot be shown that they have occupied any previous receptacle or 

 place of formation. 



"From what we at present know, we may probably assume with some 

 degree of certainty that the ' nursing ' individuals are never themselves 

 gemmiparous, but that they are born with germs in the organs in 

 which the embryos are afterwards nourished; nnd from all this it 

 appears as if the female generative organism were always divided in 

 those cases in which development by means of ' nurses ' occurs, so 

 that as in the more perfect females an ovary especially is formed, so 

 in the 'nursing' individuals a much-developed uterus is presented, 

 in consequence of which, they, as individualised uteri, have assigned 

 to them, as the object of their existence, the performance of the func- 

 tions of a uterus, and their complete formation must thus necessarily 

 precede that of the germs which are committed to their fostering care. 

 We cannot readily perceive the reason, that liecause all 'nursing' 

 individuals must be of the female sex, it should follow that all those 

 individuals which feed the young should also be of that sex, and yet 

 this seems to be the law. Anatomy shows us that the 'feeders' 

 among bees, wasps, 4a, and probably those of all insects living iu 

 regular societies, are females, whose sexual organs remain in au un.ii- 

 veloped state. They present scarcely the vestige of an ovary ; the 

 uterus is rudimentary, and all propagation consequently in the mate- 

 rial way, so to say, is rendered impossible ; the imperfection of the 

 organ does not even allow of their acting as ' nurses,' and the propa- 

 gative instinct in a physical, corporeal sense passes into a will for the 

 propagation of the species, into a nitta impelling to the feeding or 

 nourishing of the young; and the fulfilment of these impulsive duties 

 is favoured by the peculiar transformation which some of the organs 

 undergo at the expense of those intended for propagation, in order 

 that they may become adapted to the bringing up of the young. 

 Whence it follows that the development of the species in this case 

 does not take place by means of several generation!*, but through 

 several broods of the same generation. The reason of the great 

 number of ' feeders,' and for the common good of ' workers,' so that 

 they often constitute thousands, whilst the fertile individuals scarcely 

 amount tu hundreds, may be readily understood when we consider 



