438 GENERATION. SECT. XXXIX. 12. r. 



feed becomes fo much more perfect as to produce fexual organs 

 of reproduction, as the flower with its anthers and (ligma. 



This curious analogy is not only fupported by the feedling 

 buds of trees, which fucceed each other for ten or twelve gen- 

 erations, the parent buds dying in the autumn, before they be- 

 come fafficiently perfect to form the fexual organs of reproduc- 

 tion in their flower, as occurs in apple-trees ; but is alfo ob- 

 fervable in a complete infect, as in the aphis, which continues 

 to propagate for nine generations from the egg without fex ; 

 and then becomes fo perfect as to form fexual organs, and to 

 produce an oviparous progeny. Other infects, as the moths 

 and butterflies, undergo a great change of form, before they 

 acquire the property of fexual reproduction ; and probably in- 

 numerable other kinds of infects are fubject to the fame law. 



This idea of the production and changes of form of microf- 

 copic animalcules is countenanced by the fmaller kinds, never, 

 I believe, having been feen in their egg or infant itate ; and by 

 fome of them being capable of being revived in a few hours by 

 warmth and moifture after having been dry and motionlefs for 

 months, as the infect named vorticella. And laftly, from the 

 changeful forms, which fome of them affume, as that which is 

 called proteus. See Baker and Adams on the Microfcope. 



Thus as by the attractions, and aptitudes to be attracted, which 

 exift in inanimate matter, various new bodies are produced from 

 the decompofition of thofe, which previoufly exifted ; fo by the 

 appetencies to embrace, and the propenfities to be embraced, in 

 animalized matter, various new animalcules are formed from 

 the decompofition of thofe, which previoufly exifted ; owing in 

 both cafes to the immutable laws imprefled both on inanimate 

 and on organized matter by the great FIRST CAUSE. 



XII. i . CAUSE AND EFFECT may be confidered as the progref- 

 fion, or fucceflive motions, of the parts of the great fyftem of 

 Nature. The ilate of things at this moment is the effect of the 

 ilate of things, which exifted in the preceding moment ; and 

 the caufe of the ftate of things, which (hall exift in the next 

 moment. 



Thefe caufes and effects may be more eafily comprehended, 

 if motion be confidered as a change of the figure of a group of 

 bodies, as propofed in Sect. XIV. 2. 2. inafmuch as our ideas 

 of vifible or tangible objects are more diftinct, than our ab- 

 ftradted ideas of their motions. Now the change of the con- 

 figuration of the fyftem of nature at this moment muft be an 

 effect of the preceding configuration, for a change of configur- 

 ation cannot exift without a previous configuration ; and the 

 proximate caufe of every effect muft immediately precede that 



effect. 



