Alternation of generations

“ Reproduction in this group is so closely concerned with alternation of generations that it should be considered in that connection. The life histories of seven species have been studied and in every one of these cases heterogeny has been discovered. It is very likely that in most of the other species of the genus a sirnilar heterogeny exists, but it is extremely important to discover whether all of the species have this sort of life history. ”

“ Adler (1881) has definitely proved, by the breeding of successive generations, that Diastrophus rubi has no alternation of generations, and nothing known concerning emergence dates, dates of appearance of the galls, etc., indicates that we should expect heterogeny in the group. Herein these insects are more primitive, less specialized than the oak gall-wasps. ”

“ They will dwell upon it, and the generations of their children will dwell upon it, till they become sufficiently numerous to need another creation. What generation? Generations do you say, Mr. Pratt? Do you mean to say that these immortal beings are going to have posterity? ”

“ The males of most of the species (not including A. glechomæ) are known, and the sexes are about equally well represented in collections, but I have not had an opportunity to breed large enough numbers of any of the species of the genus to obtain reliable data as to the ratio in which the sexes exist. A. glechomæ may regularly reproduce agamically.
There is no alternation of generations in Aylax glechomæ and Aylax papaberis (=A. rhæadis Bouche) , as Adler proved (1881) by experimental breeding of the insects for successive generations. ”

“ In the case of other species, most likely for the majority of the oak-gall-producing Cynipidæ, only the alternate generations are siInilar, every agamic generation being succeeded by a bisexual generation, which in turn produces an agamic generation. Where this heterogeny occurs the origin and development of an agamic generation has been so involved with the origin and development of the alternation of dissimilar generations that the problem is more properly discussed in the section of this paper on the alternation of generations. ”

“ But forms, which in periods of rapid progress were severed from others after a short duration, must have impressed themselves less deeply upon the developmental history of their descendants, than those which repeated themselves unchanged, through a long series of successive generations in periods of rest. ”

“ And supposing this process were to go on, the line of descent might constantly spread out into hundreds, thousands and millions; but in each generation of descendants there would be no more individuals than in any previous generation of ancestors. The web of generations is like lattice-work or the diagonal threads in cloth. ”

“ This was conclusive proof that there is no alternation of generations with this species, and nothing known of its life history would suggest that an alternation ever occurs. By strictly isolating the females from the males at emergence and before oviposition, and by anatomical examination of the receptaculurm, Adler proved the parthenogenetic development of eggs.
{{center|Rhodites ignotus Osten Sacken
Plate XXVIII, Figures 5 to 7
Rhodites igntota Osten Sacken, 1863, Proc. Ent. Soc. Phila., II, pp. 44, 45, 49. Gillette, 1892, Ent. News, III, p. 246. Beutenmüller, 1892, Bull. Amer. Mus. ”

“ Countless generations succeed one another, occupying the soil in which the remains of older generations lie buried, each new generation springing from the one before it and bearing the marks of an inheritance that allies its individual members with other men and trees in far distant lands, and that carries them back through a seemingly endless chain of life to a remote antiquity. ”

“ The galls thus obtained were typical ignotus galls in every way resembling the galls of the parent generation. Nothing else known of the life history of the species would suggest that it possesses an alternation of generations. Ants attacked the cvnipids whaen they died after oviposition and only a single whole specimen, a male, was rescued for the collection. ”

“ Thirty-three generations go to a thousand years. There are some two hundred and sixty-four or two hundred and seventy generations intervening between you and me. Each generation makes some discovery that advances civilization a stage, the next enters on the discoveries of the preceding generations, and so culture advances stage by stage. Man is infinitely progressive, the brute beast is not. ”

“ These, by this time, will be empty; for the first generation will have sprung into life, soon to go forth, from their shadowy corner of birth, disperse over the neighbouring blossoms, people the rays of the sun and quicken the smiling hours; and then sacrifice themselves in their turn to the new generations that are already filling their place in the cradles. ”

“ If we trace cyclical reproduction to the adaptation of different developmental stages or generations to deviating conditions of life, we thus not only explain the exact and often striking agreement between form and mode of life—we not only bridge over the gap between metamorphosis and alternation of generation, but we can also understand how, within one and the same family of Hydrozoa, species can occur with or without alternation of generation, and further how other species can exist in which the alternation of generation (the production of free Medusæ) is limited to the one sex ”

“ If it be true that it takes several generations to perfect a race from a physical point of view, it is equally true that several generations are{65} needed for the development of the moral and intellectual qualities. ”

“ Or the generations might be conceived as the links of an indeterminate chain, necessarily held to each other: but suggesting not at all the idea of a living process such that its every step is fraught with eternal consequence. In a word, we incline to think that History merely goes on repeating itself, and we have to learn that History never repeats itself. ”

“ Noteworthy also, and serviceable for the progress of this same individual, wilt thou find his subdivisions into Generations. Generations are as the Days of toilsome Mankind; Death and Birth are the vesper and the matin bells, that summon Mankind to sleep, and to rise refreshed for new advancement. What the Father has made, the Son can make and enjoy ”

“ Generations succeeded Generations to no Purpose; and as all constantly set out from the same Point, whole Centuries rolled on in the Rudeness and Barbarity of the first Age; the Species was grown old, while the Individual still remained in a State of Childhood. ”

“ This principle of Reversion is the most wonderful of all the attributes of Inheritance. It proves to us that the transmission of a character and its development, which ordinarily go together and thus escape discrimination, are distinct powers; and these powers in some cases are even antagonistic, for each acts alternately in successive generations. ”

“ Smaller yet are these conceptions compared with that sublime and supreme synthesis which embraces not only the present generation of terrestrial inhabitants, but which extends longitudinally as well as laterally, extends in time as well as in space, and embraces the generations which shall grow out of the existing generation and which are yet unborn—that conception which recognises earth-life as a single process, world-wide and immortal, every part related and akin to every other party and each generation linked to an unending posterity. ”

“ You doubtless know something of the subject, how certain traits appear in families generation after generation. Accidental traits, if repeated for two or three generations, often become inherent traits. ”

“ Well,—but isn't the stature stunted, physical, as well as mental and moral, when life is forced to reproduce itself, generation after generation, among the unnatural conditions of slums and industrialism? ”

“ Of the myriads of generations which such a process of development may have occupied, perhaps the first set moved with suctorial processes, while the second gradually adopted sedentary habits, and throughout the whole of the long series, each succeeding generation must have been almost exactly like its predecessor, and must always have consisted of individuals which possessed the characters of the species. ”

“ As I understand it, he wished to inculcate the idea that one generation lays the foundation for succeeding generations. The rough affairs of life very largely fall to the earlier generation, while the next one has the privilege of dealing with the higher and more æsthetic things of life. ”

“ The changes which it may produce are not sensible within a generation—for, indeed, the very nature of the case implies that they must take many generations—not perhaps even within such a period as is covered by all authentic history. ”

“ But if, now, we breed true on the point x, destroying the reversions or backward variations for many generations, we will gradually accumulate a fund of ancestral heredity on this point which increases with every added generation, until finally the tendency to reversion becomes small. ”

“ But now—and this is a very important law of inheritance—if such a transmission of a favourable character is continued through a series of generations, it is not simply transmitted in the original manner, but it is constantly increased and strengthened, and in a last generation it attains a strength which distinguishes this generation very essentially from the original parent. ”

“ That, in the civilized world, one generation is the heir of the generations which went before it, is what no one requires to be told. Thus the discovery of the compass, of printing, and of the steam-engine, have been epochs in human knowledge from which a start was made by all civilized nations, without retrogression. ”

“ We now come to another supposed analogy, on which great stress is laid by the evolution school, and especially by Mr. Spencer. Individuals of the same family are found to be marked by striking peculiarities of structure, ancestral traits, which appear and disappear and then appear again, in successive generations. This is obviously a case where the "appropriate conditions" are all comprehended in the connection of life with life. ”

“ If the majority of these arrived at maturity and gave rise to progeny, the next generation would represent a prodigious number, and the numbers in the succeeding generations would increase so rapidly that soon there would not be room in the fresh waters of the earth to contain their descendants. ”

“ All which is clear, and all which is to my purpose is, that there is a tendency, a probability, greater or less according to circumstances, but always considerable, that the descendants of cultivated parents will have, by born nervous organisation, a greater aptitude for cultivation than the descendants of such as are not cultivated; and that this tendency augments, in some enhanced ratio, for many generations. ”

“ By this means many dark sides of human nature are specially developed and, as it were, artificially bred, and, according to the laws of transmission by inheritance, are propagated through series of generations with ever-increasing force and dominance. ”

“ In order to arrive at a more perfect decision on this head, it will be proper to consider the generation which undertakes to establish a Family with hereditary powers, apart and separate from the generations which are to follow; and also to consider the character in which the first generation acts with respect to succeeding generations. ”

“ It may here be objected that we are venturing on too uncertain ground in endeavoring to formulate any general law of the growth of habit in relation to heredity, opinions differing so much as to the relative importance to be accorded to environment and innate tendency in the formation of character, and especially as to the possibility of the inheritance, by succeeding generations, of new peculiarities not common to the species as a whole but acquired by individual parents. ”

“ The multiplication of generations is signified and set forth to notice by the repetition. Are possibly two generations to be understood, as ye are aware, my beloved brethren, and as I have before explained? for there is now a generation of flesh and blood: there will be a future generation in the resurrection of the dead. ”

“ Generation to generation, breeding ever anew; and when you die, the new stock goes on. That's the meaning of eternal life. What do you get out of it? An existence innocently and properly set towards all. ”

“ For as generation and this universe are suspended from an intellectual essence; thus, also, in the orderly distribution of souls, the liberation from generation accords with the care employed by them about generation. ”

“ He treats the unending chain of generations as if it were a single individual, and operates with his 'secular' stimulus, and with 'weak stimuli, lasting through countless generations,' as though they were a proved fact. ”

“ Each child has both a father and a mother, and two grandparents on both sides, increasing as one goes back. But, besides drawing on a much wider ancestry than the immediate parents, we have more than we inherit, or where could the law of progress operate? Each generation, each child who is born, comes into a slightly different world, fed by more experience, blown upon by fresh influences. ”

“ These species will change, therefore, generation by generation; the old sort of individual that used to prosper and dominate will fail and die out and the new sort of individual will become the rule,—until the general character of the species changes. ”