810 ANATOMY OF VERTEBRATES. 



built up, not evolved, f the brain and heart, with their append- 

 ages, the nerves and vessels, and so 011 of all the other parts of 

 the body which we do not find at first.' l His third principle is 

 merely a modification of cpigenesis, viz., ( change in form and 

 action of pre-existing parts.' 



At the present day the question may seem hardly worth the 

 paper on which it is referred to. 2 Nevertheless, ' pre-existence 

 of germs ' and ' evolution ' are logically inseparable from the idea 

 of the origin of species by primary miraculously created indi- 

 viduals. Cuvier, therefore, maintained both, as firmly as did 

 Haller. 3 It is, perhaps, one of the most remarkable instances 

 of the degree in which a favourite theory may render us blind 

 to facts which are opposed to our prepossessions. Hunter's 

 demonstrations of the epigenetic development of the blastoderm 

 and initial parts of the chick 4 were not known to Cuvier ; but 

 the analogous ones of Wolff 5 he had studied. To the phenomena 

 of the blood-lakes and their union in order to constitute the 

 6 circulus vasculosus ' of the vitellicle, Cuvier opposes the follow- 

 ing remark : ' Mais il faut necessairement admettre qu'il y avait 

 line pre existence de quelques chemins pour les pointes rouges ; 

 car en vertu de quelle force la figure veineuse serait-elle toujours 

 composee des memes vaisseaux ayant la meine direction ? Com- 

 ment ces vaisseaux aboutiraient-ils toujours au meine point pour 

 former 1111 coeur ? Tous ces phenomenes ne sont intelligibles 

 qu'autant qu'on admet quelque pre-existence.' 6 



Haller, who had made some good observations on embryonal 

 development, confessed that there was a stage in that of the chick 

 in which the 'intestinal canal was not visible ;' he would not ad- 

 mit, however, that it was not formed, or that it did not pre-exist ; 

 but affirmed that it Avas too minute to be perceived : not until the 

 head and limb-buds of the chick appeared, was the intestine 

 visibly ( evolved.' 7 



1 xx. vol. v. p. xiv. 



2 The encasement or imboxing (' emboitement ') of germs was deemed, a century 

 or more ago, to receive support from the evolution of buds and other parts of plants, 

 and from Swammerdam's discoveries in the chrysalis, not only of the parts which 

 afterwards form the butterfly, as wings, antenn?e, &c., but also of the eggs which 

 were to be laid in that phase of life. Bonnet drew an inference in favour of the 

 same view from his discovery of the numerous successive generations of Aphides, which 

 might be impregnated by a single copulation. (See, however, cxui'. pp. 27, 39.) 



3 xxvm". 4 xx. vol. v. Pis. Ixviii.-Ixxviii. 5 cccvi". 



6 cccvii". torn. iv. p. 236. 



7 "Partes animalis non noviter formantur, sed transeunt ex statu obscuro in con- 

 spicuum." xxvm". torn. viii. sectio 2da. p. 150-156. Also ' Memoire II., sur la 

 formation du Poxilet,' p. 182. 



