Chap. XXVII. PliO VISIONAL HYPOTHESIS OF PANGENESIS. 349 



CHAPTEE XXVII. 



PROVISIONAL HYPOTHESIS OF PANGENESIS. 



PRELIMINARY REMARKS — FIRST PART : — THE FACTS TO BE CONNECTED UNDER 

 A SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUC- 

 TION — RE-GROWTH OF AMPUTATED PARTS — GRAFT-HYBRIDS — THE DIRECT 

 ACTION OF THE MALE ELEMENT ON THE FEMALE — DEVELOPMENT — THE 

 FUNCTIONAL INDEPENDENCE OF THE UNITS OF THE BODY — VARIABILITY 

 — INHERITANCE — REVERSION. 



"SECOND PART : — STATEMENT OF THE HYPOTHESIS — HOW FAR THE NECESSARY 

 ASSUMPTIONS ARE IMPROBABLE— EXPLANATION BY AID OF THE HYPOTHESIS 

 OF THE SEVERAL CLASSES OF FACTS SPECIFIED 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 one another. 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 ovules, but occasionally on the mother- 

 form; how a hybrid can be produced by the union of the 

 cellular tissue of two plants independently of the organs of 

 generation ; how a limb can be reproduced on the exact line 

 of amputation, with neither too much nor too little added ; 

 how the same organism may be produced by such widely 

 different processes, as budding and true seminal generation ; 

 and, lastly, how of two allied forms, one passes in the course of 

 its development through the most complex metamorphoses, 

 and the other does not do so, though when mature both are 

 alike in every detail of structure. I am aware that my 

 view is merely a provisional hypothesis or speculation ; but 



