1885.] 
A cclimatisation. 
205 
we trace along with the infinite chain of monocellular gene- 
rations a corresponding number of individuals of a higher 
order, — polyzoic individuals, — which, unlike the mono- 
cellulars, do not emanate directly from each other, but only 
through the mediation of mono-cellular beings. These 
individuals of a higher order, alone, have a physiological 
end a natural death. The monocellular generations — • 
germ-cells — are potentially as immortal as the Protozoa or 
other independent, monocellular organisms, since they are 
not absorbed in their buds, the Metazoa, but split off from 
them, living on in the interior of such Metazoa, whence 
they derive protection and nourishment. 
VI. ACCLIMATISATION. 
By J. W. Slater. 
'Sp' HIS ungainly word has in practice a very different 
meaning from that which its etymology would show. 
As commonly used it means the introduction of any 
alien plant or animal into a country through human agency. 
Whether such immigrants had to be gradually adapted to 
their new home by a series of physiological modifications, 
or whether they found it equally congenial with their 
mother-country, — or possibly more so, — is not the question. 
Another glance at the word may be useful. It seems to 
imply, if not directly to connote, that the main reason why 
any animal or plant flourishes in one country, but perishes 
in another, is some difference in the climate, in the geo- 
graphical sense of the term. In other words, it conveys the 
impression that the animal and vegetable population of a 
country depends solely upon its mean or its extreme temper- 
ature at different seasons of the year, upon atmospheric 
pressure, or upon degree of moisture. Now without ignoring 
the influence of these physical conditions of life we must 
remember that they are not the sole, noi even the leading, 
agencies in determining the flora 01 launa of a legion. 
There are good physical reasons why humming-birds are not 
found in Iceland, Greenland, or Siberia. There are no such 
