SECT. 3] AND EIGHTEENTH CENTURIES 131 



it self unto?" He gives a clearly deterministic account of develop- 

 ment. "Take a bean, or any other seed and put it in the earth, and 

 let water fall upon it; can it then choose but that the bean must swell? 

 The bean swelling, can it choose but break the skin? The skin 

 broken, can it choose (by reason of the heat that is in it) but push 

 out more matter, and do that action which we may call germinating? 

 Can these germs choose but pierce the earth in small strings, as they 

 are able to make their way? . . . Thus by drawing the thrid carefully 

 along through your fingers, and staying at every knot to examine 

 how it is tyed ; you see that this difficult progresse of the generation 

 of living creatures is obvious enough to be comprehended and the 

 steps of it set down; if one would but take the paines and afford 

 the time that is necessary to note diligently all the circumstances in 

 every change of it. . . . Now if all this orderly succession of mutations 

 be necessarily made in a bean, by force of sundry circumstances and 

 externall accidents ; why may it not be conceived that the like is also 

 done in sensible creatures, but in a more perfect manner, they being 

 perfecter substances? Surely the progresse we have set down is much 

 more reasonable than to conceive that in the seed of the male there 

 is already in act, the substance of flesh, bone, sinews, and veins, and 

 the rest of those severall similar parts which are found in the body 

 of an animall, and that they are but extended to their due magnitude 

 by the humidity drawn from the mother, without receiving any 

 substantiall mutation from what they were originally in the seed. 

 Let us then confidently conclude, that all generation is made of a 

 fitting, but remote, homogeneall compounded substance upon which 

 outward Agents, working in the due course of Nature, do change it 

 into another substance, quite different from the first, and do make it 

 lesse homogeneall than the first was. And other circumstances and 

 agents do change this second into a third, that third, into a fourth; 

 and so onwards, by successive mutations that still make every new 

 thing become lesse homogeneall than the former was, according to 

 the nature of heat, mingling more and more different bodies together, 

 untill that substance bee produced which we consider the period of 

 all these mutations." This passage is indeed admirable, and well 

 expresses the most modern conception of embryonic development, 

 that of the ovum as a physico-chemical system, containing within 

 itself only to a slight and varying degree any localisation answering 

 to the localisation of the adult, and ready to change itself, once the 



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