It has often been said by naturalists that each cell of a plant has the actual or potential capacity of reproducing the whole plant; but it has this power only in virtue of containing gemmules derived from every part.
Pure gemmules in combination with hybridised gemmules would lead to partial reversion.
We shall presently see how well the long-continued transmission of undeveloped gemmules explains many facts.
Precisely the same view may be extended to one of the higher animals; although in this case many thousand gemmules must be thrown off from the various parts of the body.
We see that the reproductive organs do not actually create the sexual elements; they merely determine or permit the aggregation of the gemmules in a special manner.
The gemmules or capsular buds of the Polycyttaria were first accurately described by Richard Hertwig (L.
The gemmules or capsular buds (hitherto described as "extracapsular bodies") are developed on the surface of young central capsules before these had secreted a membrane.
The difference is between the mere absence of gemmules and the presence of modified gemmules.
Finally, variations might arise from the superabundance of certain gemmules and the deficiency of others, and from the varying potency of the gemmules contained in the sperm and ovum.
He calls the collection of gemmules in the fertilized ovum the "stirp.
The pangenetic answer to this objection is that gemmules multiply and are transmitted during long series of generations.
The ovum remains comparatively unaffected by changes in the body; but it receives from the sperm, with which it unites, gemmules from such tissues in the male as were undergoing special modification.
In this case the gemmules of the parental and grandparental tail are simply absent.
And since the parental cells are subject to modification, transmitted through the gemmules to the reproductive elements, it is clear that there is abundant room and opportunity for varietal combinations.
Darwin's hypothesis was frankly and simply organic--the gemmules are little germs.
Where the maternal and paternalgemmules are of equal potency, the cell resulting from their union will be a true mean between them; where one or other is prepotent, the resulting cell will tend in a corresponding direction.
The hypothesis also assumes that these gemmulesneed not in all cases develop into cells, but may lie dormant, and be transmitted from generation to generation without producing a noticeable effect until a case of atavism occurs.
In winter the sponge dies down and the gemmules are set free in the water.
The asexual mode of reproduction of the fresh-water sponge by gemmules has already been described.
The ocean sponges also reproduce asexually either by forming interiorgemmules or external buds.
The whole idea of the passage of gemmules from the modified parts of the body into the germ-cells is based upon the unproved assumption that acquired characters can be transmitted.
We must therefore assume the existence of a special gemmule for each group of molecules, and thus the innumerable gemmules of Darwin’s theory must be imagined as increased by many millions.
What an incomprehensible number of gemmules must meet in a single sperm- or germ-cell, if each of them is to contain a representative of every molecule or group of molecules which has formed part of the body at each period of ontogeny.
Footnote 98: Galton’s experiments on transfusion in Rabbits have in the mean time really proved that Darwin’s gemmules do not exist.
According to this hypothesis, every unit or cell of the body throws off gemmules or undeveloped atoms, which are transmitted to the offspring of both sexes, and are multiplied by self-division.
Moreover, these gemmulesare supposed to tend to aggregate themselves, and to reproduce in certain definite relations to other gemmules.
The emission of thegemmules takes place, or may take place in all states of the cell.
We have seen also that in certain cases a similar multitude of gemmules must be included also in every considerable part of the whole body of each organism, but where are we to stop?
The existence of the gemmules is a first unknown element; the propagative affinity of the gemmules is a second; their germinative affinity is a third; their multiplication by fission is a fourth--and what an unknown element!
The gemmules possess two sorts of affinity, one of which might be called propagative, and the other germinative affinity.
Yet on the hypothesis of Pangenesis, the zoospore of an alga must contain gemmules from all the cells of the parent algæ, and from all the parts of all their less remote ancestors in all their stages of existence.
That such a complete collection of gemmules is aggregated in each ovum and spermatozoon in most animals, and in each part capable of reproducing by gemmation (budding) in the lowest animals and in plants.
If then the hypothesis of pangenesis is well founded, that rite ought to be now absolutely or nearly superfluous from the necessarily continuous absence of certain gemmules through so many centuries and so many generations.
The gemmules must be very small indeed, but it may be suggested that the molecules of matter are smaller still, so this fact is no objection to the theory.
It is supposed that fecundation is chiefly necessary to give to the gemmules the requisite amount of nourishment to insure development.
Darwin states that in his treatment of hybridism in terms of gemmules he is practically following Naudin's treatment of the same theme in terms of "essences.
Gemmules are supposed to be thrown off by every unit; not only during the adult state, but during each stage of development of every organ; but not necessarily during the continued existence of the same unit.
Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation into buds, or into the sexual elements.
Now, suppose that instead of these hypothetic gemmules we endow the units with memory in ever so slight a degree, how simple the explanation of all these facts becomes!
The gemmules with brilliant corpuscles had almost disappeared; we could see but very few, and those now consisted of the refractive bodies alone, the bulk of the vibrios accompanying them having undergone some process of re-absorption.
From these gemmules we have ultimately produced vibrios, ready to reproduce others by the process of transverse division for a certain time, to be themselves encysted, later on.
They contain comparatively few gemmules and were evidently in a vigorous condition as regards vegetative growth.
The structure of the gemmules of this species differs considerably from that in any other known species of the genus, in which these structures are usually adherent and devoid of a true pneumatic coat.
The production of gemmules may have been brought about owing to the sponge being choked by the more vigorous growth of S.
The gemmulesgerminate immediately and their contents spread out over the old skeleton, secrete a chitinous membrane and begin to build up a new sponge.
Pavement layer Adherent gemmules arranged close together in a single layer at the base of a sponge.
Zykoff found that in Europe gemmules kept for two years were still alive and able to germinate.
Gemmule-spicules, which form a characteristic feature of the Spongillidae, are very seldom absent when the gemmules are mature.
Carter found that if he cleaned gemmules with a handkerchief and placed them in water exposed to sunlight, they germinated in a few days; but in Calcutta gemmules of Spongilla alba var.
Gemmules and fragment of the skeleton of Spongilla cinerea (from type specimen), x 35.
The gemmules of sponges growing in lakes are sometimes deficient in spicules.
This species is easily distinguished from its allies of the subgenus Euspongilla by its adherent gemmules with their (usually) multiple apertures and rough external surface.
Both eggs and buds are produced by freshwater sponges (the latter rarely except by one species), while their gemmules attain an elaboration of structure not observed in any other family of sponges.
The latter consist of single gemmules and not of a pair in one case.
The Darwinian hypothesis of Pangenesis rests on the conception that all inheritable properties are represented in the cells by small invisible particles or gemmules and that these gemmules increase by division.
Perhaps we might retain Darwin's self-multiplying gemmules without supposing them to be thrown off by the cells, which will no longer be credited with two modes of multiplication.
The size, strength, health and other good or evil qualities of the cells could hardly fail to exercise a marked and corresponding effect upon the size and quality of the reproductive gemmules thrown off by those cells.
Hence, when the germs or gemmules which achieve development are either better or worse than the residue, the qualities transmitted to offspring will be of an inverse character.
We know that the paternal half of the reproductive elements does not enter the ovum till a comparatively late stage in its history, and it is quite possible that maternal elements or gemmules may also enter the ovum from without.
On the contrary, in all ordinary cases of mutilation the purely atavistic elements or gemmules would be set free from any modifying influence of the non-existent or mutilated part.
Galton restricts the production of gemmules by the personal structure to a few exceptional cases, and would evidently like to dispense with pangenesis altogether, if he could only be sure that acquired characters are never inherited.
Many obvious facts compelled Darwin to suppose that vast numbers of the reproductive gemmules in an individual are not thrown off by his own cells, but are the self-multiplying progeny of ancestral gemmules.
The answer probably is that all the gemmules of the mutilated or amputated part are gradually attracted to the diseased surface during the reparative process, and are there destroyed by the morbid action.
It has often been said by naturalists that each cell of a plant has the potential capacity of reproducing the whole plant; but it has this power only in virtue of containing gemmules derived from every part.
In this case and in all others the proper gemmules must combine in due order with pre-existing nascent cells, owing to their elective affinities.
But considering how minute the molecules are, and how many go to the formation of the smallest granule of any ordinary substance, this difficulty with respect to the gemmules is not insuperable.
The sexual elements, on the other hand, do not include such nascent cells; and the male and female elements taken separately do not contain a sufficient number of gemmules for independent development, except in the cases of parthenogenesis.
But we are far from knowing whether the gemmules of all the units are free and separate from one another, or whether some are from the first united into small aggregates.
We must believe, as previously shown, that severalgemmules are requisite for the development of each cell or unit.
Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation into buds or into the sexual elements.
The gemmules derived from each part or organ must be thoroughly dispersed throughout the whole system.
One cannot say what gemmules of thigh and proboscis may not have got into the neutral bees' stomachs, if they assimilate their food sufficiently, and thus into the larva.
Weismann, on the other hand, rejects the doctrine ofgemmules in toto.
That the development of a new organism, out of the fusion of two such packets of gemmules, is due to a summation of all the developments of some of the gemmules which these two packets contain.
But it differs from gemmules and further resembles germ-plasm in all the following particulars.
It only remains to add that the degree of stability has been proved in not a few cases to be less than even the theory of gemmules might anticipate.
Why then should it be deemed inconceivable that, where all such things can pass, gemmules can do so likewise?
That gemmules are thrown off by all physiological cells, not only during the adult state of the organism, but during all stages of its development.
Therefore, while the theory of gemmules can freely entertain the doctrines of Lamarck, the theory of germ-plasm excludes them as physiologically impossible, in all cases where sexual reproduction is concerned.
Ruggles Geddes and Thomson Gemmules Genital ducts Gigas, Oenothera Gillichthys Gipsy moth Goltz and Ewald Gonads, hormones of Goodale, H.
That in all cases the development ofgemmules into the form of their parent cells depends on their suitable union with other partially developed gemmules which precede them in the regular course of growth.
That the development of a new organism out of the fusion of two such packets of gemmules is due to a summation of all the developments of some of the gemmules which these two packets contain.
An ovum above, full of gemmules (only three of which are represented) develops into an individual made up of cells, three of which are shown.
One can see how the gemmules formed by the body cells will be influenced by any change in these.
Among all the known forms of gemmules we find a variety which are intermediate, all of which show, when brought into a normal condition of development, the same proportion, and the same germination, as those we first described.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "gemmules" in a variety of sentences. We hope that you will now be able to make sentences using this word.
