352 Is Organic Variation Fortuitous ? [May, 
variety better adapted to the surrounding conditions than 
the then prevailing type ; secondly, the accident that this 
superior animal escapes destruction before it has had time to 
transmit its qualities ; and thirdly, the accident that it 
breeds with another specimen good enough not to neutralise 
the superior quailties of its mate.” 
A still more important argument is drawn from structure 
in advance of function. It is obvious that Natural Selection 
can only preserve such varieties as are immediately and 
direCtly useful to the organism in which they occur. Yet, as 
Mr. Murphy shows by a number of well-seleCted examples, 
there are cases “where structure has been laid down as a 
preparation for function before the function could be brought 
into aCtion, as truly as the shipwright when he lays the keel 
on the land intends the future ship to float on the water.” 
Thus in the metamorphosis of Crustaceans one particular 
stage — the so-called Zoea phase — is characterised by a pro- 
longed abdomen calculated for future utility, though for the 
time being rather an incumbrance. Elsewhere the author 
asks, of what use can a dorsal groove and an incipient carti- 
laginous band be to Ascidian larvae ? Yet, if we regard 
these creatures as representing the common ancestors of the 
Vertebrates and Ascidians, we have here the first outlines of 
the vertebral column essential to the former. The transition 
from the swim-bladder to the lungs, from the fins to legs 
with toes, and from the reptile’s fore leg to the bird’s wing, 
are also, on the hypothesis of Natural Selection, beset with 
difficulties. We can scarcely imagine any intermediate 
stages between the two which would not be useless, even if 
not positively injurious, to the animal in which they might 
occur. Mr. Murphy expresses the opinion that this argu- 
ment is new, and that, if taken up by thorough anatomists 
and embryologists, “ instances of structure in anticipation of 
function might be found everywhere in the organic world.” * 
The phenomena of mimetism, or organic mimicry, have 
generally been considered as affording strong evidence in 
favour of the Darwinian view. But it is difficult to under- 
stand how the first slight variations in the direction of ap- 
proximating a defenceless animal to some formidable species 
could be of such essential utility to the former as to ensure 
its preservation by Natural Selection. A further very 
formidable difficulty is that the mimicking form is — and if 
* A somewhat similar argument, at least as far as concerns the dangers of 
intermediate stages, may be found in the “Quarterly Journal of Science” 
(vol. v., p. 32g). The instance there given is, however, much less happy and 
conclusive than the cases adduced by Mr. Murphy. 
