380 



PROVISIONAL HYPOTHESIS 



Chap. XXVII. 



reproduces the for 



the part whence derived 



B 



this non-diffusion of the gemmules from bud to bud may 



cily app 



t, depending, as we shall hereafter see, on the 

 first-formed cells in the buds. 



The assumed 



ticular 



ffinity of each -gem mule for that par 



11 which precedes it in the order of development 



supported by many analogies 



In 



production the male and female elen 



dinary cases of 



a mutual 



affinity for each other : thus, it is believed that about ten 

 thousand species of Composite* exist, and there can be no doubt 

 that if the pollen of all these species could be, simultaneously 



ssively, placed 



of any one species, this 



ould elect with unerring certainty its own pollen. This 



capacity 



onderful 



have been ac- 

 roup of plants 



On any 



quired since the many species of this 



branched off from a common pro 



nature of sexual reproduction, the protoplasm contained within 



the ovules and within the sperm-cells (or the " spermatic force " 



of the latter, if so vague a term be preferred) must act on each 



other by some law of special affinity, either during or subse- 



so that 



ponding parts alone 

 mi a short-horned 



quently to impregnation, 



affect each other ; thus, a calf produced "fi 



cow by a long-horned bull has its horns and not its horny hoofs 



affected by the union of the two forms, and the offspring from 



birds with differently coloured tails have their tails and 

 their whole plumage affected. 



The various tissues of the body plainly show, as many phy- 

 siologists have insisted, 36 an affinity for special organic sub- 

 stances, whether natural or foreign to the body. We see this 

 in the cells of the kidneys attracting urea from the blood ; in 

 the worrara poison affecting the nerves ; upas and digitalis the 

 muscles ; the Lytta vesicatoria the kidneys ; and in the poisonous 



■s 



;er of many diseases 

 h, glanders, cancer, 



pox 



fever, hooj 



d hydrophobia, affecting certain 



definite parts of the body or certain tissues or glands. 



The affinity of various parts of the bodv for each other durin 



36 Paget, 'Lectures on Pathology,' 294; Claude Bernard, ' Des Tissus 

 p. 27; Virchovv, 'Cellular Pathology,' Vivants,' pp. 177, 210, 337; Mailer's 

 translat. by Dr. Chance, pp. 123, 126, 'Physiology,' Eng. translat, p. 290. 





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