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Show 402 PROVISIONAL IIYPOTHESIS CHAP. XXVII. h t t"on during many ages of previously remarked, than t e re en I d nc to the production rudimentary organs, or ev~n only of~ ten e y that all dormant of a rudiment · but there 1s no reason to suppose £ . E , gemmules wo~ld be transmitted and propagate~ or;~m.b xcessively minute and numerous as they are behefve l~fi et, .an . l d . lona course o moe 1 ca Ion infinite number denvec' urmg a b • lcl t b and descent from .each cell of each progemtor, cou no o ' ' ' . h d b the oraanism. On the other hand, supported or nouns e Y 0 ul d I. t does not seem I. mpr.o b ab le that. certain gemm es, un er 1 . . . favourable con dr. ti.o ns, sh ou ld be retamed and go. on mu. hplymg . cl th others Finally on the views here for a longer peno an · ' . d f 1 g1. v en . 1 . orne clear insight mto the won er u we c01'tam Y gam s h · fact th' at t h e ch 1'l d may depart from the type of bot Its parents, and resem ble 1. ts gr.a. .n dparents' or ancestors removed by many generations. Conclusiun. The hypothesis of Pangenesis, as appli~cl to the several grea~ c1 a sses of 1.£' a cts J·ust discussed ' no doubt IS extr. emely complex, b ut so assure dly ai·e the facts · The assum. ptwns, however, o.n h. 1 tl hypothesis rests cannot be considered as complex m w rc1 1e . . b ·a any ex t reme de0a r·ee ~ namely ' that al.l orgamc .. um. ts,. es1 es_ having the power, as IS generally admitted, of .growmg by self d!.V I·S ·I On, thr ow off fr·ee and minute atoms of therr contents, t.h at I·S gemmu1 e s. These multiply and aob ·gregate themselves mto buds and the sexual elements ; their development depends on their union with other nascent cells or units; ~nd they ar~ capable of transmission in a dormant state to success~ve generatwns. In a highly organised and complex ammal, the gemmules thrown off from each different cell or unit throughout .the body must be inconceivably numerous and minute. Each umt of each part as it changes during development, and we know that some inse~ts undergo at least twenty metamorphoses, ~ust throw off its gemmules. All organic beings, .moreover, mclude man.y dormant gemmules derived from theu g:·andpare~ts and r more remote progenitors, but not from all the1r progemtors. These almost infinitely numerous and minute gemmules must ~e included in each bud, ovule, spermatozoon, and pollen-.gram. Such an admission will be declared impossible; but, as prevwusly CHAP. XXVII. OF PANGENESIS. 403 remarked, number and size are only relative difficulties, and the eggs or seeds produced by certain animals or plants are so numerous that they cannot be grasped by the intellect. The organic particles with which the wind is tainted over miles of space by certain offensive animals must be infinitely minute and numerous; yet they st-rongly affect the olfactory nerves. An analogy more appropriate is afforded by the contagious particles of certain diseases, which are so minute that they float in the atmosphere and adhere to smooth paper; yet we know how largely they increase within the human body, and how powerfully they act. Independent organisms exist which are barely visible under the highest powers of our recentlyimproved microscopes, and which probably are fully as large as the cells or units in one of the higher animals ; yet these organisms no doubt reproduce themselves by germs of extreme minuteness, relatively to their own minute size. Hence the difficulty, which at first appears insurmountable, of believing in the existence of gemmules so numerous and so small as they must be according to our hypothesis, has really little weight. The cells or units of the body are generally admitted by physiologists to be autonomous, like the buds on a tree, but in a less degree. I go one step further and assume that they throw off reproductive gemmules. Thus an animal does not, as a whole, generate its kind through the sole agency of the reproductive system, but each separate cell generates its kind. 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. If our hypothesis be provisionally accepted, we must look at all the forms of asexual reproduction, whether occm ·ring at maturity or as in the case of alternate generation during youth, as fundamentally the same, and dependent on the mutual aggregation and multiplication of the gemmules. The regrowth of an amputated limb or the healing of a wound is the same process partially carried out. Sexual generation differs in some important respects, chiefly, as it would appear, in an insufficient number of gemmules being aggregated within the separate sexual elements, and probably in the presence of certain primor·dial cells. The development of each being, including all the 2 D 2 |