8 
notwithstanding great changes in the external circumstances under 
which it lived, he so weighty in the case of the Mammoth, who 
was, geologically speaking, quite a late comer on the earth, and has 
been for some time extinct, how much more pressing will he the 
argument to be derived from some of the lower forms of life, 
which appeared much earlier in the world’s history, and are still in 
existence. When Professor Huxley, in his lecture on chalk, de- 
livered in Norwich, told us that he could detect no difference 
between the Globigerina of the chalk formation, and the same 
shell brought up from the mud of the Atlantic at the present time, 
he seemed to me to state a fact proving a persistency of species in 
one instance, while change went on in others, very damaging to 
any theory of evolution, and the only explanation on this point 
that I have been able to obtain from the advocates of such a theory 
has been, that as Globigerina lives at the bottom of the sea, in 
great depth of water, the conditions of its life might perhaps, after 
all, not have changed so very much since the chalk period. But 
this explanation no longer holds good ; it has been shown quite 
recently, by the researches of the “Challenger” expedition, that 
Globigerina is, to a great extent, a surface-living animal. Now I 
suppose that no one will believe that the conditions affecting a 
minute surface living shell have not varied very much during and 
since the deposition of that enormous chalk bed which lies beneath 
our feet as we sit here to-night, a thousand feet in thickness, and 
which has been succeeded by the variation in temperature described 
by Dr. Falconer, so that if the Mammoth deserves a Dicyclotherian 
epithet, surely Globigerina may claim to be called a “ many-cycled ” 
shell. 
But even this example of persistence of type fades into insig- 
nificance before a newly-reported example in a low form of vegetable 
life. If the observations of the Count of Castracane on Diatoms 
found in coal should be confirmed, some forms of Diatoms have 
remained virtually unaltered since the carboniferous era. Now, if 
this should prove to be the fact, these forms must have survived 
enormous alterations of condition, so enormous, that if external 
circumstances really are the causes and the controllers of change of 
