BODILY CHARACTERISTICS INCONSPICUOUSNESS 285 



SPECIALIZED GENERAL RESEMBLANCE. The animals so far 

 mentioned harmonize generally with the background against which 

 they are seen, but other instances are known where the form and 

 coloration are such as to make the creature appear part and 

 parcel of some special object upon which it lives. Such are 

 some cases which have been described of association between 

 certain Corals and Sea-Snails. There is, for example, a North 

 American Coral (Leptogorgia virgulata] which in shallow water 

 is of an orange-yellow colour, but of deep-reddish tint in deeper 

 water, the position of the individuals making up the colony being 

 marked by white spots. A Sea-Snail (Ovulum uniplicatuin) lives 

 upon the branches of this Coral, with which it harmonizes precisely 

 in colour, being orange-coloured in one case, red with white spots 

 in the other. Curiously enough, a similar close relation has been 

 noticed between a Coral and a Sea- Snail (Gorgonia verrucosa and 

 Ovulum patulum) which live in British seas, both animals being 

 red in colour. The Snail in this latter case (and no doubt in the 

 other as well) is doubly benefited, for the Coral is distasteful to 

 fish, and the Snail consequently has a good chance of escaping 

 the dangers of a too close inspection. Large specimens are often 

 to be seen in museums of a Coral (Gorgonia) which protects 

 Brittle-Stars in much the same way, these holding on to the 

 Coral by twining the tips of their slender arms round its branches. 

 A similar association is recorded between a rose-coloured Aus- 

 tralian Sponge and a small species of Sea-Slug. Sponges,' it 

 may be noted, are notoriously inedible, which is, of course, an 

 additional benefit to the mollusc. 



GENERAL RESEMBLANCE IN EGGS AND YOUNG. The harmon- 

 izing by means of form and colour with the usual surroundings, to 

 which the name of General Protective Resemblance has been given, 

 is by no means confined to adult forms, for it is exemplified by 

 various earlier stages in existence. These have perhaps been 

 more fully worked out in Birds and Insects than in other groups, 

 and one or two examples taken from these must suffice. Birds* 

 eggs, when laid in concealed places, free from observation, are 

 commonly white, but when exposed to view are more or less 

 coloured or marked, or it may be both. And the plumage of such 

 fledglings as run about on the ground is usually speckled or 

 mottled to harmonize with the surroundings, which renders them 

 extremely difficult to see, especially if the little creatures crouch 



