306 ANIMAL DEFENCES 



projecting, perhaps as a warning to Gurnards and other pre- 

 daceous Fishes, which prey upon the Dragonet (Callionymus 

 fyra), that is not unlike it and has similar habits, though quite 

 devoid of poisonous properties. Annandale (in the paper already 

 quoted) applies this explanation to the Globe -Fishes (genus 

 Tetrodon, &c.), "which have earned the name of Balloon- Fish 

 among Europeans, and . . . Pillow- Fish among Malays, by the 

 manner in which they gulp down air into their stomachs, so 

 causing the brilliant coloration of many of them to become con- 

 spicuous, and also the spines with which they are armed to be 

 erected." 



Numerous instances of warning coloration are to be found 

 among the Protochordates. Some of the compound Ascidians, 

 for example, are very brightly coloured, and this is associated 

 with an unpleasant odour. This correlation of facts suggested 

 to Garstang that they are probably unpalatable to Fishes, and a 

 series of experiments conducted by him proved this actually to 

 be the case. A better example of the scientific method could 

 scarcely be found: hypothesis based on facts, and then confirmed 

 by experiment. 



The different species of Acorn-headed Worms (Balanoglossus) 

 are more or less brightly coloured and endowed with an unplea- 

 sant odour, which makes it probable that they too are possessed 

 of unpalatable qualities. 



Warning Colours of Molluscs. The bright tints of certain 

 Gastropods undoubtedly have a warning significance, though, as 

 in other cases, it is necessary to watch the animals in their natural 

 surroundings before coming to a definite conclusion, for colours 

 and colour-schemes which in themselves are extremely striking 

 may notwithstanding be well adapted to effect concealment when 

 their possessor is "at home". A good example described by 

 Herdman is that of the Sea-Slug (Nudibranch) Eolis, the upper 

 surface of which, as in so many of its kind, is beset with tentacle- 

 like projections (cerata) of brilliant colour, which in this particular 

 case do not harmonize with the natural surroundings. When it 

 is added that the tips of the cerata are provided with stinging cells 

 much like those of Jelly- Fishes and Sea- Anemones, it is not 

 surprising to learn that actual experiment proved Eolis to be 

 unpalatable to fishes. 



Striking colours were proved by Garstang to be associated 



