ANIMAL POWERS OF OFFENSE AND DEFENSE. 357 



thinking at first sight that the "butterflies themselves have been at- 

 tacked by real fungi." 



The walking-stick insects, as they are called, in their turn imitate, 

 in the skeleton-like structure of their bodies, the appearance of dried 

 twigs ; and it is a singular fact that even in their awkward, ungainly 

 manner of walking, the resemblance to the chance movements of 

 twigs is clearly perceptible ; the mimicry being rendered more real- 

 istic through this latter phase. Then, also, we find certain harmless 

 groups of moths imitating closely the outward appearance of species 

 of stinging bees and hornets. And one remarkable case of mimicry 

 is the well known instance of some perfectly inodorous South Ameri- 

 can butterflies, which perfectly reproduce the external appearance 

 of other butterflies which emit a most offensive odor; the reason 

 assigned for this latter phase of mimicry being the very feasible one 

 that the inodorous forms are protected from the attacks of birds 

 by their resemblance to their strong-smelling neighbors. As a 

 last instance of this curious phase of animal organization, we may 

 note the example furnished by those curious little fishes, the Hip- 

 pocampi, or sea-horses so named from the obvious resemblance 

 of the form of the head to that of a horse the bodies of which be- 

 come covered with long streamers of certain kinds of seaweed ; so 

 that, when these fishes rest amid the seaweed-covered nooks of their 

 marine grottoes, the presence of their streamers serves to render de- 

 tection by their enemies no easy matter. 



Referring to the explanation, if such can be afforded, of these mi- 

 metic resemblances, there can be little doubt that, viewed as to its 

 ultimate use and purpose, the condition of mimicry serves in the most 

 effective manner as a means of defense and protection to the animals 

 so endowed. The resemblance of the colors of birds to that of their 

 habitat presents an obvious instance of this purpose ; as also does 

 the more complicated example of the imitation, by scentless butterflies, 

 of their odorous neighbors. But, as regards the exact means whereby 

 the condition of mimicry is induced and perfected, or concerning the 

 exact causes of its assumption and development, natural history sci- 

 ence, in its practical aspect, remains silent ; although the bolder march 

 of theory and speculation may indeed lead us for a little way toward 

 the solution of the problem. At any rate, there can be no difficulty 

 to our clearly appreciating the workings of a great law of purpose 

 and design in the production of mimicry, as serving to protect the 

 weak and less powerful against stronger and better-provided animals. 



Turning now to some lower forms of animal life, we find in such 

 forms as the Hydros, or common fresh-water polyps, the zoophytes, 

 sea-anemones, jelly-fishes, and allied forms, excellent examples of very 

 specific means of defense and offense in animals. Within the tissues 

 of the bodies of the foregoing organisms, when these tissues are mi- 

 croscopically examined, numerous little sacs or cells, varying in size 



