qr CRITICISMS ON “ THE ORIGIN OF SPECIES” 95 
tion, however, is distinguished very essentially from Darwin’s 
: by the entire absence of the principle of useful variations and 
_ their natural selection : and my fundamental conception is this, 
' that a great plan of development lies at the foundation of the 
origin of the whole organic world, impelling the simpler forms 
to more and more complex developments. How this law 
operates, what influences determine the development of the 
eggs and germs, and impel them to assume constantly new 
- forms, I naturally cannot pretend to say ; but I can at least 
adduce the great analogy of the alternation of generations. If 
_ a Bipinnaria, a Brachiolaria, a Pluteus, is competent to produce 
the Echinoderm, which is so widely different from it; if a 
hydroid polype can produce the higher Medusa ; if the vermiform 
Trematode ‘nurse’ can develop within itself the very unlike 
_ Cercaria, it wili not appear impossible that the egg, or ciliated 
embryo, of a sponge, for once, under special conditions, might 
become a hydroid polype, or the embryo of a Medusa, an 
Echinoderm.” 
It is obvious, from these extracts, that Pro- 
fessor Kolliker’s hypothesis is based upon the 
supposed existence of a close analogy between the 
phenomena of Agamogenesis and the production 
of new species from pre-existing ones. But is the 
analogy areal one? We think that it is not, and, 
by the hypothesis cannot be. 
For what are the phenomena of Agamogenesis, 
stated generally? An impregnated egg develops 
into a sexless form, A ; this gives rise, non-sexually, 
to asecond form or forms, B, more or less different 
from A. Bmay multiply non-sexually again ; in 
the simpler cases, however, it does not, but, acquir- 
ing sexual characters, produces impregnated eggs 
from whence A, once more, arises. 
