117 



But, this can be accepted only in the case where one believes that species 

 are formed only through the fixation of characters acquired by adaptation or 

 direct influence, which characters are ever diverging. When we think of 

 several other causes of the formation of sp3cies, such as crossing and mutation, 

 we can not but be forced to conclude that it is impossible to arrive at blood - 

 affinity through indirect methods. Tha latter conclusion can be easily under- 

 stood by one who accepts the participation theory. It is only in some special 

 case that we can see blood - relationship through the study of resemblance 15 . 

 As blood - relationship is of course one of the natural relations manifested by 

 organisms, it should certainly app3ar in one phase of the dynamic system. 

 But, it can not be definitely stated that blood - relationship is the only criterion 

 for constituting a natural system. ENGLEE goes on to say !) : 



Es kat die Erfakrung gelekrt, daS SuBerlich. oft sAr ithnliche Organismen nur 

 cine entfemte Venvandtsckaft besitzen. 



This. is indeed true. That is why I should say that a real natural relation 

 is so and so in external form, but at the same time is manifested differently 

 in blood - relationship. In this resp3ct, his opinion differs from mine. Again 

 he says :!) : 



So ist man zu der Erkenntnis gelangt, dafi einzellige, Icugelige, also iUiSerlick sehr 

 aknlicke Organismen nicht bloB sehr versckiedtmen Familien, sondern auch verscliie- 

 denen Kla&sen und Abteilungen angekoren konnen. 



In my opinion, this will not do. According to my idea, if organisms are very 

 similar in their external forms, they should be taken into the same group. 

 In some special case where we know their blood - relationship exactly, it will 

 be all right to arrange them according to this criterion. The latter arrangement 

 is sometimes, as ENGLER states above, very different from that made according 

 to the standard of external forms. But tliis does no harm to our natural 

 system. The difference follows from the difference in the criterion. The 

 natural system should, therefore, be a dynamic one which manifests different 

 phases when viewed from different standpoints. Further he proceeds to 

 say: 



So gelangt man znr Feststelhing von Verwandtsckaftskreisen, deren system a ti- 

 scker Bang lediglick danack bestimmt \vird, bis zu welckem Grade 



1) LOTST, P. J. I.e. 2) ENGLKB, A. I.e. p. IX. 3) ENGLHB, A. I.e. p. 



