PKOTECTIVE AND AGGRESSIVE RESEMBLANCE 341 



itself the effect of some structural modification, however impossible 

 to detect, in nervous tissue. In the Australian Phyllopteryx 

 eques, a fish which is closely related to the curious sea-horse 

 (Hippocampus) of our own coasts, we get precisely the same 

 idea, so to speak, carried out in a different manner. Both 

 Hippocampus and Phyllopteryx live amongst seaweed, to which 

 they attach themselves by means of their curious prehensile 

 tails. Hippocampus (Fig. 173) exhibits no special resemblance 



FIG. 174. 



FIG. 173. 



FIG. 173. A Sea-horse (Hippocampus antiquorum}, X f. (From a 



photograph.) 



FIG. 174. Phyllopteryx eques, attached to seaweed. (From Giinther's 

 "Study of Fishes.") 



to its surroundings, but in Phyllopteryx (Fig. 174) the body is 

 covered with cutaneous outgrowths which float out in the water 

 like fronds of seaweed and doubtless effect a most satisfactory 

 disguise. This is certainly a less troublesome plan than that of 

 dressing up in clothing borrowed from the outside world. 



The well known colour changes of the chamaeleon and of 

 various flat fishes, not to mention numerous other instances 

 which might be cited from different groups of the animal king- 

 dom, are due to a complex apparatus, controlled by the nervous 



