162 THE AMERICAN NATURALIST. [VoL. XXXII. 
dice, of scientific conservatism, and other subtle reasons, and 
in part the result of his trained scientific mind accustomed to 
think more or less in one channel, not allowing itself to specu- 
late too freely on too few facts. On the whole, however, the 
theory of descent was contrary to his whole nature and training; 
we can in this regard only liken the career of this great natu- 
ralist to one of his own ‘closed types.” There are zoologists 
who attempt the impossible; who would refer, for example, the 
origin of vertebrates to Crustacea or to Limulus, overlooking 
the fact that these classes are the final terms in lines of devel- 
opment and are fully completed. So the special creation idea 
was unproductive, and a Darwin was needed to open men’s eyes 
to new conceptions, to illumine well-known facts from a fresh 
point of view. 
But it should never be forgotten that Agassiz from the 
beginning of his career advocated certain doctrines which under- 
lie the theory of descent. The first of these is the founda- 
tion of the biogenetic law. He insisted that the development 
of the individual is an epitome of that of the order or class to 
which it belonged, though unfortunately he stopped short of 
the logical outcome of such a generalization; z.e., that there is 
an organic or genetic connection between the forms composing 
‘the class. 
The second principle is the parallelism between the geologi- 
cal succession of animals and their respective rank in the 
present period. He points out repeatedly that the lower types 
preceded the higher. For example, in the Crustacea the grada- 
tion of forms presents the most perfect coincidence with the 
order of succession of these animals in past geological ages. 
His “lowest ” forms are the generalized types of zoologists of 
the present day, and his “higher ” types the more specialized. 
All this prepared the minds of his students to accept the 
truth of a process of evolution of life-forms from the general- 
ized to the specialized types. His ‘ embryonic,” ‘ synthetic,” 
and “ prophetic ” types are in many cases the ancestral types 
of the modern evolutionist. His embryonic types ‘ represent 
in their whole organization early stages of the growth of higher 
representatives of the same type.” He maintained that “the 
