[December : 
776 
Working v. Fighting. 
us against the popular error of ascribing to such selection 
the origin of the variations upon which it has afterwards to 
aft. In one case Mr. Wallace advances statements which 
have the semblance at least of discrepancy. On p. 73 he 
remarks that “ reptiles appear at first sight to be as much 
dependent on land for their dispersal as mammalia, but 
they possess two peculiarities which favour their occasional 
transmission across the sea the one being theii greater 
tenacity of life, and the other their oviparous mode of repro- 
duction. M Yet on p. 319 we read : — “ To this cause we must 
impute our comparative poverty in mammalia and reptiles— 
more marked in the latter than the former, owing to their 
lower vitality and smaller powers of dispersal.” 
Mr. Wallace’s sections on the permanence of the distribu- 
tion of land and water and on the causes of glaciation must 
be passed over, as I find that they will be considered sepa- 
rately in some future number of the “ Journal of Science. 
Prof. Semper’s introductory chapter is fraught with useful 
lessons which are sometimes left out of view even by the 
more advanced student. The author considers the distinc- 
tions between adaptive and hereditary peculiarities. He 
shows that parts, which from their adaptive character have 
little or no meaning in determining the affinities of the 
higher systematic groups, acquire a very great diagnostic 
value for smaller divisions, within which they must rank as 
hereditary. Hence it is impossible to draw an a priori dis- 
tinction between adaptive and hereditary characters. He 
shows the necessity for the naturalist, of a “ physiology 
of organisms ” superadded to the physiology of organs 
which has been vitiated by being ordinarily treated and, 
studied exclusively with reference to medical practice. I his 
is a deplorable fact. It may be inquired what would be the 
state of chemistry if cultivated merely from a pharmaceutical 
point of view, or of astronomy if confined to the service of navi- 
gation ? If it be asked what is such a “ physiology of organ- 
isms ” the author replies that it comprehends all those laws 
which are perceived on investigating the vital relations of 
different animal species to each other, and to the conditions 
bv which they are, as such, preserved, destroyed, or trans- 
muted. As an instance of the problems with which this 
branch of science has to deal he mentions the discovery ol 
the causes which have led, in vertebrate animals, to the 
development of the two pairs of limbs and two only. 
There is very much more in this work well deseiving 01 
special notice, such as the account of the eyes— of the true 
vertebrate type — found in the back of the molluskous genus 
