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From these ground-fish, in the strictest sense of the word, 

 there is only a step to such fishes as select the crevices and 

 hollows of rocky coasts for their place of abode , when they 

 usually lie in wait for prey in a similar manner to the fish 

 before described. To this class belong the curious Dragon-heads 

 (Scorpaena), clumsy fish with thick heads and big mouths, 

 large spiny fins and peculiarly developed skin-appendages, in the 

 form of little ragged, feathery leaves and spines. These fish 

 jam their bodies into the corners of the rocks, and can so ex- 

 actly imitate the colour of the rocks that any one not aware 

 of this power may stand some time before a tank full of Scor- 

 paenae before seeing one. In the dark corners, many resemble 

 a fragment of rock overgrown with delicate plants so perfectly , 

 that this faculty alone must to a great degree protect them 

 from their enemies and enable them to surprise their prey. 

 We find this principle of protective imitation in a great num- 

 ber of animals ; it is so with the inhabitants of the desert, 

 which are almost all yellow like the sand; and with the white 

 polar and alpine animals , some of which for example the 

 Snow-hen , even change their coat according to the season. 

 It is so with the transparent Medusae and pelagic animals of 

 the ocean, whose transparency protects them from pursuit. In 

 some animals, the principle is carried out by their resemblance 

 to plants, or to animals better protected than themselves, either 

 by weapons or poisonous glands , or by their insignificance. 

 Certain flies imitate the habitus of bees and wasps, and trop- 

 ical butterflies imitate those of their relations who are better 

 prepared than themselves for the struggle for life. This inter- 

 esting phenomenon is called " mimicry, " and it has been 

 proved to exist in marine animals of very different classes. It 

 is a striking proof of the theory of the gradual transformation 

 of animals and vegetables by natural selection of better o?' 

 ganized forms. 



Akin to the Dragon-heads, in its manner of life, is the Go- 

 by (Gobius niger), a little black ground-fish of clumsy form, 

 which always lies at the bottom of the tank, usually in some 

 rocky cavity, a bunch of algae, or such like. It is, however, 

 fonder of moving than the Scorpaena. In the sea , during 

 spawning time , it leaves its hiding-place and digs a roomy 

 dwelling among the roots of the sea-weed, in which it drops 

 its eggs. The male is the architect, and lies at the entrance 

 of the nest, enticing the female to approach. When the latter 

 has laid her eggs , the male immediately impregnates them, 



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