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141 
small as to be practically worthless ; but Wallace has now shown, in 
aseries of diagrams giving the exact measurements of numerous animals, 
that nearly every part of an animal varies very largely, usually ten or 
twenty, and sometimes even twenty-five per cent. of the average size 
-of the varying part, and that variation, instead of being the exception, 
must now be taken as the rule. One must also remember, in the case 
-of insects, how quickly they increase, and how short the life of an 
individual insect is, comparatively few living beyond a year ; and then 
“the severe struggle for existence, only a very small percentage of those 
born living to propagate their kind ; and then the enormous period of 
‘time during which these modifications may have been going on. In 
the Lias of the Swiss Jura upwards of a hundred species of beetles 
have been found, as well as representatives of other orders ; and in 
->some of the calcareous bands of the Lower Lias insects are so abundant 
‘that these are known as insect beds. The earliest known butterfly was 
found in the Lower Oolite. In a paper read before the Geological 
‘Society of London, Mr. T. M. Reade estimates that the series of post- 
-glacial deposits on the coasts of Lancashire and Cheshire represent 
-a lapse of time of not less than fifty-seven thousand five hundred 
"years, and, according to Dr. Croll, two hundred and ten thousand 
_years ago the Glacial period was at its maximum, and before this there 
-were the ancient Glacial epochs, which, on astronomical considerations, 
he computes at three million years back. Many geologists, I believe, 
-consider them all to have occurred during Tertiary ages ; but even 
-allowing them to have been in the Cretaceous period, we have our 
-ancestral butterfly immensely older still, dating back to the Stonesfield 
«slate. 
A vote of thanks to the reader was moved by Mr. SuHum, 
-and a short discussion ensued in which the Rev. E. T. Stupgs and 
ithe SECRETARY took part. 
The session of 1890-91 was opened by the VICE-PRESIDENT 
(Canon Ellacombe) on the afternoon of Wednesday, 17th 
December, with an instructive address on the vegetation of the 
past year. The substance of the address, which was given vivé 
#oce, was the following :— 
After a few words by way of preface, explaining his reasons for the 
absence of a formal paper, he stated that the past year was an excep- 
