SOCIETIES. 163 
deposited ; and the leaf closes over the ova when the appendages are 
withdrawn. The discussion on the two similar species, Plebius argus 
and P. argyrognomon was resumed and concluded.—Mr. H. St. J. 
Donisthorpe read a paper “On the Origin and Ancestral Form of 
Myrmecophilous Coleoptera.”—Mr. W. L. Distant communicated a 
paper on “ Rhynchota Malayana.”—Mr. J. H. Collin communicated a 
paper by Mr. Wesché “On the Antenne of Diptera, and the Present 
Classification of the Nemocera, with two subsidiary sections bearing 
on the latter subject.” —Mr. G. A. K. Marshall then read a paper en- 
titled “On Reciprocal Mimiery. A Rejoinder to Dr. F. A. Dixey.” 
Dr. Dixey had taken the view that within the limits of a Miillerian 
association every species exercises a mimetic influence upon every 
other, the amount of the influence depending upon its dominance, 
which is determined by its numbers, distastefulness, and general 
notoriety. Thus, as between any two species, the mimetic approach 
would be mutual and result in an interchange of characters. This 
interchange would be proportionate to the relative dominance of the 
two species; where this is unequal, the weaker species would take 
on, to a considerable extent, the superficial appearance of the 
stronger, while the latter would adopt only some small characters 
from its mimic; but where the dominance is equal, the interchange 
would be equal, so that this would constitute the optimum condition 
for the production of reciprocal mimicry. On the other hand, Mr. 
Marshall contended that this gravitational conception of mimicry was 
really based on a false analogy and was at variance with the real 
principle of Miller’s theory. While admitting the theoretical possi- 
bility of mimetic interchange, he urged that a logical application of 
Miiller’s argument would lead to the view that mimetic approach 
would be one-sided only, that is, from a weaker species towards a 
stronger and even in an opposite direction; further, that when the 
relative dominance of the two species was equal, the mere operation 
of Miiller’s factor would produce no mimetic effect until some other 
factor had first produced a condition of inequality. On this view 
mimetic interchange would never be mutual and simultaneous, but 
would only result from a complete reversal of the relative dominance 
of the two species during the production of the mimetic resemblance. 
For this process he had suggested the name of “ Alternate Mimicry.” 
Mr. Marshall said also that he was compelled to reject entirely Dr. 
Dixey’s new hypothesis as to the ‘function of the double aposeme,”’ 
because it completely left out of consideration the differences and re- 
semblances between the various forms regarded from the standpoint of 
general facies ; he contended that resemblance in general effect was of 
the first importance in considering mimetic relationship, and that this 
new hypothesis was liable to be extremely misleading on account of 
the exaggerated significance which it attached to the merely partial 
resemblance which might be said to exist between two species 
possessing a single conspicuous feature in common but differing 
markedly in other respects. Moreover, not only was the theoretical 
position of Reciprocal Mimicry very unsatisfactory and unconvincing, 
but, further, the cases which had been cited as proving its actual 
occurrence in nature appeared open to serious criticism. For while 
in some cases the facts did not appear to justify the assertion that an 
