| OCR Text |
Show 356 LAWS OF VARIATION. CHAP. XXVI. two causes analogous varieties often arise. When we reflect on the several £o rego·m g Ia ws, 1· mper£ e c tly as we. understan. d them, and when we bear in mind how much remams t~ be. chs-d d t be Sllrprised at the extremely mtr1cate covere , we nee no . manner in which our domestic productions have vaned, and still go on varying. CHAP. XXVII. PROVISIONAL HYPOTHESIS OF PANGENESIS. 357 CHAPTER XXVII. PROVISIONAL HYPOTHESIS OF PANGENESIS. PRELIMINARY REMARKS.- FIRST PART;- THE FACTS TO BE CONNECTED UNDER A SINGLE POL"<T OF VillW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION- THE DIRECT ACTION OF THE MALE ELEMENT ON THE FEMALE- DEVELOPMENTTHE FUNCTIONAL INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE BODY - VARIABILITY- INHERITANCE- REVERSION. SECOND PART :-STATEMENT OF THE HYPOTHESIS -HOW FAR THE NECESSARY ASSIDfPTIONS ARE IMPROBABLE- EXPLANATION BY AID OF THE HYPOTHESIS OF THE SEVERAL CLASSES OF FACTS SPECIFmD IN THE FIRST PART- CONCLUSION. IN the previous chapters large classes of facts, such as those bearing on bud-variation, the various forms of inheritance, the causes and laws of variation, have been discussed; and it is obvious that these subjects, as well as the several modes of reproduction, stand in some sort of relation to each other. I have been led, or rather forced, to form a view which to a certain extent connects these facts by a tangible method. Every one would wish to explain to himself, even in an imperfect manner, how it is possible for a character possessed by some remote ancestor suddenly to reappear in the offspring; how the effects of increased or decreased use of a limb can be transmitted to the child; how the male sexual element can act not solely on the ovule, but occasionally on the mother-form; how a limb can be reproduced on the exact line of amputation, with neither too much nor too little added; how the various modes of reproduction are connected, and so forth. I am aware that my view is merely a provisional hypothesis or speculation; but until a better one be advanced, .it may be serviceable by bringing together a multitude of facts which are at present left disconnected by any efficient cause. As Whewell, the historian of the inductive sciences, remarks:-" Hypotheses may often be "of service to science, when they involve a certain portion of " incompleteness, and even of error." Under this point of view I venture to advance the hypothesis of Pangcnesis, which im- |
