388 LOTSY, CURRENT THEORIES OF EVOLUTION. 
The impossibility to apply the experimental test in most cases 
makes phylogenetic deductions from material which we can only 
compare — and in the case of fossils we can do nothing else — 
so very uncertain. All conclusions as to continuous variation or 
orthogenesis, based on even the finest graded series between two 
conspicuously different types, are mere speculations because the. 
occurence of intermediates does not reveal their mode of origin, 
so that from such an occurrence the conclusion may not be drawn 
that the observed intermediates are transitional forms between the 
extreme types. Nor is it legitimate to refer to breaks in such a. 
series of intermediates as to „missing links,” because no form may 
ever have filled the gap which we observe. An example may illu- 
strate what has been said about intermediates. 

Fig. 1. Two species of Pheasants and their hybrids ; from left to right: Feather of 
Gennaeus Horsfeldii; two feathers of hybrids G. Horsfieldii X G. lineatus; 
feather of G. lineatus; three feathers of hybrids G. lineatus X G. argentatus; 
feather of G. argentea; all from the experiments of GHIGI. 
We can arrange the feathers of certain pheasants in such a way 
that they make a magnificent series of intermediates between 
Gennaeus argentatus and Gennaeus lineatus, or between the latter 
and Gennaeus Horsfieldit and we may feel inclined to read this 
series as one of transition, between the species named, revealing 
continuous variation or even orthogenesis. Moreover, we may collect 
such intermediate specimens in regions between those in which 
the species mentioned occur, which of course would strengthen the 
view that these intermediate specimens are transitions between them. 
Unfortunately however, for those, who have ascribed the origin 
of these intermediate forms to a process of variation, continuous 
or orthogenetic, the members of the fine series of intermediates, 
re rit 


CIM ET 



ED ARE 
Non 

N 
