296 ANIMAL DEFENCES 



on a sudden alarm. This Is the case, for instance, with the 

 young of some Plovers (see p. 286). 



A good instance of special protective resemblance among the 

 lower Vertebrates is afforded by Australian species {Phyllopteryx 

 eques, and two others) of the curious fishes known as Sea- 

 Horses, of which a less remarkable genus (^Hippocampus) is 

 commonly represented in museums. These Australian forms, 

 which may be as much as a foot long, are laterally flattened, 

 and attach themselves by means of their curly tails to pieces of 



Fig. 480. — Australian Sea-Horse [Phyllopteryx eqiies) 



brown sea-weed (species of Fticus). Giinther (in The Shidy of 

 Fishes) says of them: — "Not only their colour closely assimilates 

 to that of the particular kind of sea-weed which they frequent, but 

 the appendages of their spines seem to be merely part of the fucus 

 to which they are attached ". (Fig. 480.) 



Herdman and others have described a number of very inter- 

 esting cases of protective form and colour among Sea-Slugs. 

 Some of these (notably Doto coronata and Dcjidronotus arbor- 

 escens) have their upper surfaces richly studded with brightly- 

 coloured projections (cerata), which at first sight serve to make 

 them conspicuous, but in reality so closely resemble the branch- 

 ing colonies of zoophytes among which they live as to make them 

 difficult for their enemies to detect. 



Many of the most striking of the special protective resem- 

 blances so far described are to be found among Insects in various 



