372 



PEOVISIONAL HYPOTHESIS 



Chap. XXVIL 



plants, and can combine with that of another and distinct 

 plant, giving rise to a new being, intermediate in character. 

 We know also that the male element can act directly on the 

 partially developed tissues of the mother-plant, and on the 

 future progeny of female animals. The formative matter 

 which is thus dispersed throughout the tissues of plants, 

 and which is capable of being developed into each unit or 

 part, must be generated there by some means ; and my chief 

 assumption is that this matter consists of minute particles 

 or gemmules cast off from each unit or cell.*^ 



But I have further to assume that the gemmules in their un- 

 developed state are capable of largel}'' multiplying themselves 

 by self -division, like independent organisms. Delpino insists 

 that to " admit of multiplication by fissiparity in corpuscles, 

 *' analogous to seeds or buds ... is repugnant to all analogy." 

 But this seems a strange objection, as Thuret** has seen the 

 zoospore of an alga divide itself, and each half germinated. 

 Haeckel divided the segmented ovum of a siphonophora into 

 many pieces, and these were developed. Nor does the extreme 

 minuteness of the gemmules, which can hardly diifer much in 

 nature from the lowest and simplest organisms, render it 

 improbable that they should grow and multiply. A great 

 authoritj^. Dr. Beale,'*^ says " that minute yeast cells are 

 " capable of throwing off buds or gemmules, much less than 

 " the ToVo'oo ^^ ^^^ ^^^^ ^^ diameter ;" and these he thinks are 

 " capable of subdivision practically ad infinitum." 



A particle of small-pox matter, so minute as to be borne by 

 the wind, must multiply itself many thousandfold in a person 

 thus inoculated ; and so with the contagious matter of scarlet 

 fever.*^ It has recently been ascertained *^ that a minute 

 portion of the mucous discharge from an animal affected with 



** Mr. Lowne has observed (' Jour- 

 nal of Queckett Microscopical Club,* 

 Sopt. 23, 1870) certain remarkable 

 changes in the tissues of the larva of 

 a fly, which makes him believe " it 

 ** possible that organs and organisms 

 " are sometimes developed by the 

 *' aggregation of excessively minute 

 " gemmules, such as those which Mr. 

 " Darwin's hypothesis demands." 



44 



'Annales des Sc. Nat.,' 3rd 

 series, Bot., tom. xiv., 1850, p. 244. 



** ' Disease Germs,' p. 20. 



*^ See some very interesting papers 

 on this subject by Dr. Beale, in 

 ' Medical Times and Gazette,' Sept. 

 9th, 1865, pp. 273, 330. 



*'' Third Report of the R. Comm. 

 on the Cattle Plague, as quoted in 

 ' Card. Chronicle,' 1866, p. 446. 



