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species which are most nearly allied, to trace the ancestors from 
which the more recently developed species have sprung, to trace again 
the ancestors of these, and so on to a common base from which a 
large family has sprung, and then, extending the view, to reach at 
last the common ancestor of the Order. 
It is quite clear that, in doing this, a great many considerations 
must arise. If we see two species which are very similar in 
appearance in the imaginal (or in the larval) state, there is a prima 
facie reason for supposing that the similarity is the outward sign of a 
real alliance, or blood-relationship, as it were ; but, if we find that 
the larvffi are entirely dissimilar, that the pup® present marked 
differences, then we may safely assume that the similarity of the 
imagines is quite fortuitous, that the similarity has been brought 
about probably by similar necessities, and is possibly entirely due to 
natural selection, the two similar facies having been reached by 
entirely different routes. The separation of fortuitous resemblances 
from real relationships is one of the most difficult factors that the 
biologist has to meet, for one has to carefully search out facts by 
tedious and laborious methods, and weigh them carefully when found, 
before arriving at a conclusion. The slightest trace of slip-shod work 
in such an enquiry as this must necessarily prove fatal. 
It may be well here to see if we can understand, at least in part, 
the lines on which our specialists work. Examine carefully a newly- 
hatched larva of Vanessa urticae , Mamestra brassicae, any Tortricv, or 
member of the genus Tinea (which devours your woollens, cloths and 
such like articles). You will find that they all have a close general 
resemblance in the arrangement of the little chitinous, hair-bearing 
buttons or tubercles, as they are called, different as they may 
afterwards become with each ecdysis of the larvae. Now compare 
them with the adult larvae of Cossus, Zeuzera. Sesia, &c., and you will 
find the same general appearance that you have already observed in 
the young larvae just examined. Now these characters are general to 
most young larvae, and to some more or less adult ones, hence a larva 
which possesses these characters is looked upon, and spoken of, as a 
generalised form, whilst those which vary from this form are looked 
upon as being more or less specialised according to the extent of the 
difference exhibited. 
Now, it must be evident, if, as we suppose, the larvae of Hejnalus , 
Cossus , Sesia, and newly-hatched larvae in general, represent the most 
ancient form of larva, that those which differ most markedly from 
these are the more altered and specialised when compared with the 
original form, and by comparison of any larva then with those forms 
which we consider the more generalised, we can gauge the degree and 
direction of the specialisation which the larva has undergone from 
the original ancestral condition. 
Mr. Dyar has taken the tubercles as the larval character on which 
his work has been chiefly based, and he finds that modifications, in 
the direction of consolidation of these in various ways, take place in 
the main groups along fairly fixed and definite lines. If, therefore, a 
species, hitherto supposed to belong to a certain group, fails to present 
the characters belonging to this group, Mr. Dyar naturally questions 
