324 Dr. Frederick A. Dixey on 
footing, any departure from which might be attended with 
danger to itself; while the only part played by the former 
is to shelter itself under as close an approximation to the 
aspect of the model as circumstances permit. 
We may now take the case of a species possessing 
a nauseous flavour, and requiring some means of adver- 
tisement in order to make its inedibility available for 
purposes of protection. 'T'wo courses may be said to lie 
open for such a species. First, it may seek advertise- 
ment by acquiring a conspicuous and easily recognised 
aspect of its own, distinct from that of any others; or, 
secondly, it may obtain a share in the notoriety already 
attaching to some dominant inedible form by assimilating 
its aspect to that of the latter, instead of striking out a 
new line for itself. An examination of the lepidopterous 
fauna of such a region as the neotropical makes it certain 
that the latter of these methods, viz., the method of 
‘“Miillerian mimicry,” has been very extensively fol- 
lowed. Its advantages, as compared with the former 
method, are obvious. In the first place it assists the 
memory of predaceous foes by keeping at a low figure the 
number of distinct inedible types to be learned and so 
avoided, and in the second place it benefits at least two 
species at the same time instead of one, and both have 
therefore an interest in keeping it up; for inasmuch as in 
this case, as distinct from that of Batesian mimicry, the 
mimic is inedible as well as the model, the results of 
experimental tasting will be uniformly the same, and will 
be favourable to the immunity of both species. It 
follows that (1) there is no such limit as exists in 
Batesian mimicry to the number either of individuals or 
species forming a Miillerian group. An assemblage of 
this latter kind is only strengthened, not weakened, by 
fresh accessions; all being alike inedible, and so all 
contributing to the common safety. (2) The benefit 
of Miillerian association being mutual, there is a distinct 
reason, which we saw does not exist in the case of 
Batesian mimicry, for the model to help on the process of 
assimilation by itself advancing to meet the mimic. 
To summarise the foregoing. Every conspicuous and 
distasteful form is a centre of attraction for other forms, 
whether edible or inedible; but in the former case 
(Batesian mimicry) the mimetic attraction is limited in 
operation, and acts only in one direction, influencing 
