48 THE BIOLOGICAL PROBLEM OF TO-DAY 



limb. From a bud of embryonic tissue there are 

 elaborated in the one case whole vertebrae, with their 

 muscles and tendons, and part of the spinal cord 

 with its ganglia and nerves, in the other case, the 

 numerous, differently-shaped, skeletal pieces of the 

 hand or foot, with their appropriate muscles and 

 nerves. The regeneration, moreover, is in strict 

 conformity with the characters of the species con- 

 cerned. Thus, from the facts of regeneration also, 

 we must infer that cells in the vicinity of these 

 casual wounds possess not only the special qualities 

 which they possess as definite parts of a definite 

 whole, but also the characters of the whole, and 

 thus have the power of becoming buds, from which 

 a complicated part of the body may be reproduced 

 with the appropriate characters of the species. 



FOURTH GROUP OF FACTS. THE PHENOMENA OF 



HETEROMORPHOSIS. 1 



Of all the facts brought forward here, the 

 phenomena of heteromorphosis perhaps bear most 

 strongly in favour of my conception, and offer 



1 In tliis section upon heteromorphosis I rely upon the follow- 

 ing treatises, which have appeared recently. Loeb, Untersuchungen 

 zur pliysiologischen Morphologic der Thiere. Organ-bildung und 

 Wachsthum. Heft, 1 and 2 (1891-1892). H. de Vries, Intra- 

 ccttulare Pangenesis (1889). H. Driesch, Entiviclclungsmechanische 

 Studien, i. -vi. ; Zeitschrift f. ivissenschaft, Zool., vol. liii. -Iv. The 

 same, Zur Theorie der thierischen FormUldung. Biol. Central- 

 blatt, vol. xiii., 1893. Chabry, Contribution a I' embryologie 

 normale et Urcdologiqiie des Ascidies simples. Jour, de VAnat. et 

 de Physiol. (1887). Wilson, Amphioxus and the Mosaic Theory. 

 Journal of Morpli. (1893). See also Anatomischer Anzeigcr 

 (1892). 



