372 PROVISIONAL HYPOTHESIS Chap. XXVU. 



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. 43 



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

 developed state are capable of largely 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 44 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. JSor does the extreme 

 minuteness of the gemmules, which can hardly differ much in 

 nature from the lowest and simplest organisms, render it 

 improbable that they should grow and multiply. A great 

 authority, Dr. Beale, 43 says " that minute yeast cells are 

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

 " the touVou of an inch in 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. 46 It has recently been ascertained 47 that a minute 

 portion of the mucous discharge from an animal affected with 



43 Mr. Lowne has observed (' Jour- 44 'Annales des Sc. Nat.,' 3rd 



nil of Queckett Microscopical Club,' series, Bot., torn. xiv., 1850, p. 244. 

 Sept. 23, 1870) certain remarkable 4i ' Disease Germs,' p. 20. 



changes in the tissues of the larva of i6 See some very interesting papers 



a rly. which makes him believe ;< it on this subject by Dr. Beale, in 



" possible that organs and organisms ' Medical Times and Gazette,' Sept. 



" are sometimes developed by the 9th, 1865, pp. 273, 330. 

 " aggregation of excessively minute 47 Third Report of the R. Comm 



k ' gemmules, such as those which Mr on the Cattle Plague, as quoted in 



" Darwin's hypothesis demandt." • Gard. Chronicle,' 1866, p. 446. 



