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 eques] 



brown sea-weed (species of Fucus). Glinther (in The Study 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 Dendronotus 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 



