268 
by a stage during which no great change occurred for a long 
time, the latter stage would, in successive generations, encroach 
upon the former stage more quickly than the former stage 
encroached upon its predecessor; and ultimately the short 
stage must disappear. Thus there would be gaps in the 
ontogenetic record of phylogeny. 
Tue Eximrnation or Dissruinar Staces. 
The unequal action of the law of earlier inheritance would 
appear not to be the only cause of such gaps in the ontogenetic 
record. The influence of economy also plays a part. When 
the phylogenetic series, by some developmental change—as for 
instance, reversion—acquires characters different to its last 
stage, but approximately similar to some preceding stage— 
when, say, the adolescent and senile stages are practically 
similar, while the adult stage is dissimilar—there is a tendency 
in the later members of the phylogenetic series to dispense 
with the dissimilar stage by the law of economy of growth; and 
in the course of their ontogeny, by passing directly from one 
similar stage to the other similar stage, to avoid the double 
change which would be required by the production of the 
dissimilar stage. This tendency becomes very potent when 
the dissimilar stage has been considerably shortened by “the 
unequal action of the law of earlier inheritance.” This phe- 
nomenon may be referred to shortly as the “elimination of 
dissimilar stages.” 
Tur Mopirication oF Haruier INHERITANCE. 
There is yet another phase of the laws connected with 
earlier inheritance to be alluded to; and it obviously depends 
on a similar force to that which governs the “ eliminiation 
of dissimilar stages.” Ontogenetical investigations have shewn 
me that although the embryonic and infantile stages of life 
are the morphological representations of what were the adult 
stages of some more or less remote ancestors, yet that, in 
certain cases and under certain conditions, they do not represent 
these formerly-adult stages with complete accuracy. 
ef 
