Prof. Carl Vogt on some Darwinistic Heresies. 59 



place in phylogenetic speculations, and ani/ ph?/Iogenetic tree 

 tchi'ch does not take it into account is hy that fact alone errone- 

 ous or null. 



The above-mentioned facts lead us, in the second place, to 

 conclude that there is convergence of characters. As early 

 as 1874, at the meeting at tlie French Association at Lille, 

 Prof. Vogt brought forward a thesis suggested by the investi- 

 gation of various parasites {Entoconcha, Sacculina, Redia), 

 and formulated in the following terms : — " Prolonged adapta- 

 tion to a restricted but predominant cause gradually effaces 

 the divergent characters of types and finally effects, if not 

 their union, at least their approximation to such a degree that 

 the distinctive characters even of the great divisions of the 

 animal kingdom become entirely unrecognizable." 



There is reason to widen this proposition. Do we not see 

 this convergence take place in a nuniber of series of animals 

 living in perfect freedom ? The more we study animals, even 

 those the phylogeny of which we cannot know, the more we 

 come to facts which lead to conclusions establishing a multiple 

 origin for the groups which are united in our classification. 

 Has not Prof. Hackel, the monophyletist j^ar excellence^ been 

 led by his investigations upon the Medusee to ascribe to 

 them a diphyletic origin ? 



We see this convergence manifested not only in entire 

 groups, but also in organs. Starting from the limbs of the Ghe- 

 lonians and seals we see set up series of modifications leading 

 to the paddles of the Halisaurians, Cetacea, and Sirenia. 

 Have not these last two orders, differing completely in their 

 dentition and other anatomical characters, indicating very 

 different stocks, been brought together solely because their 

 limbs are constructed in the same fashion ? 



If, then, convergence is established in many instances, it is 

 our business to examine how it is brought about. So far as 

 we know from palteontological and embryonic investigations, 

 all metamorphoses take place in three different ways : — 



1. By the reduction and final loss of primordial characters. 



2. By the excessive and unilateral dev^elopment [einseitige 

 Entioicklung) of other cliaracters which often originally 

 existed only roughly sketched out. 



3. By changes of function (Functtonswechsel), which are so 

 frequent, and to which M. Dohrn long since called the atten- 

 tion of naturalists, without finding much response. Change 

 of functions also implies the separation of parts originally 

 united, and the fusion of other parts originally separated. 



Prof. Vogt cannot enter into the details which prove these 

 assertions j but, if they are true, it necessarily follows from 



