G1 
practically, yet cannot help denying it, and for the following reasons : — The 
proof is rested on geological evidence. What is that evidence? We are 
presented with forms of living things which were and are not. Their ex- 
tinction may not be doubted. But where is the geological proof of successive 
introductions of other forms of life ? Is it because of that class of facts 
which says the Pleuronectidse are not found in the earliest strata where fish 
is discovered, and must therefore have been a subsequent introduction ? In 
dealing, most especially, with geological evidence, three things should be care- 
fully borne in mind — that absence is no proof of non-existence ; that presence 
is no proof of recent introduction ; and that so comparatively small an area 
has been subjected to geological research, inferences should be received with 
the greatest caution. In seeking after epochs of introduction, the evidence 
of the rocks is purely negative, and negative witness is no witness at all. 
A few years since, palaeontologists found no bird in any older deposit than 
the tertiary, affording the loose geological negative evidence of the introduc- 
tion of birds during that period. The Archseopterix macrurus was afterwards 
detected in the upper oolite, and part of the skeleton of another gull had 
been found in the greensand of the cretaceous series. From these and similar 
facts, I caimot agree with Mr. Warington that the practical geologist must 
necessarily believe in fresh introductions of life since the first beginning of 
creation. To fix the date of an event in the tertiary rocks, from negative 
testimony, and then find it must have occurred in the secondary, if not 
earlier, shows the value of such geological inference ; and only those carried 
away by the fascinations of science can subject their reason to their imagi- 
nation. 
Mr. Warington takes up another part of the subject. He says, “I wish now 
to notice a misrepresentation of the Darwinian theory ” ; and he proceeds to 
observe that my argument goes upon the assumption that, if a variety thrown 
off by the parent plant perpetuate itself, it is a species ; but if it revert or 
die out, it ceases to be a variety. And he brings this example in refutation : 
“ Now, take the simple case of man. A Negro perpetuates himself, and a 
Chinese, and a North- American Indian, with all their differences, most 
exactly ; yet we firmly believe they have all sprung from one original stock.” 
If I had intended to have expressed the opinion that a variety could per- 
petuate itself so as to set up another species , how could I have said on the 
preceding page, “ I consider that the perfect and complete forms were those 
created, from which varieties cannot be raised into species ” ? And again, the 
two lines immediately before Mr. Warington’s extract show the intended 
meaning of the whole passage : — “ If varieties could be converted into species, 
extended time, such as Mr. Darwin requires, seems a most unnecessasy step 
in the process.” If they could, plainly tells my belief they could not. How- 
ever, I am afraid the sentence on which he comments is ambiguous — no light 
fault in scientific discussion. 
Alluding to the necessity of our culinary vegetables and florists’ flowers 
being continued by constant care in the state to which artificial culture has 
brought them, Mr. Warington says I have dealt unjustly with Mr. Darwin’s 
