448 OCEANOGRAPHY, BIONOMICS, AND AQUICULTURE. 



flush with the general surface. The integument of the mollusk is, both 

 in general tint, and also in surface markings, very like the Ascidian 

 colony with its scattered ascidiozooids. This is clearly a good case of 

 protective coloring. Presumably, the Lamellaria escapes the observa- 

 tion of its enemies through being mistaken for a part of the Leptocliii urn 

 colony; and the Leptoclinum being crowded like a sponge with minute, 

 sharp-pointed spicules is, I suppose, avoided as inedible by carnivorous 

 animals, which might devour such things as the soft, unprotected mol- 

 lusk. But the presence of the spicules evidently does not protect t\ie 

 Leptoclinum from Lamellaria, so that we have, if the above interpreta- 

 tion is correct, the curious result that the Lamellaria profits by a 

 protective characteristic of the Leptoclinum, for which it has itself no 

 respect, or, to put it another way, the Lieptoclinum is protected against 

 enemies to some extent for the benefit of the Lamellaria, which preys 

 upon its vitals. 



It is to my mind no sufficient objection to theories of protective and 

 warning coloration that careful investigation may from time to time 

 reveal cases where a disguise is penetrated, a protection frustrated, an 

 offensive device supposed to confer inedibility apparently ignored. 

 We must bear in mind that the enemies, as well as their prey, are 

 exposed to competition, are subject to natural selection, are undergoing 

 evolution; that the pursuers and the pursued, the eaters and the eaten, 

 have been evolved together, and that it may be of great advantage to 

 be protected from some even if not from all enemies. Just as on land, 

 some animals can browse upon thistles whose " nemo me impune 

 lacessit" spines are supposed to confer immunity from attack, so it is 

 quite in accord with our ideas of evolution by means of natural selec- 

 tion to suppose that some marine animals have evolved an indifference 

 to the noxious sponge or to the bristling Ascidian, which are able, by 

 their defensive characteristics, like the thistle, to repel the majority of 

 invaders. 



Although we can keep and study the Littoral and Laminarian animals 

 at ease in our zoological stations, it may perhaps be questioned how 

 far we can reproduce in our experimental and observational tanks 

 the conditions of the Coralline and the Deep-mud zones. One might 

 suppose that the pressure — which we have no means as yet for supply- 

 ing 1 — and which at 30 fathoms amounts to nearly 100 pounds on the 

 square inch, and at 80 fathoms to about 240 pounds, or over 2 hundred- 

 weight on the square inch, would be an essential factor in the life con- 

 ditions of the inhabitants of such depths, and yet we have kept half a 

 dozen specimens of Calocaris macandrew, dredged from 70 to 80 fath- 

 oms, alive at the Port Erin Biological Station for several weeks; we 



following up M. Regnard's experiments, some mechanical arrangement whereby 

 water could he kept circulating and aerated under pressure in closed tanks might he 

 devised, and ought to he tried at some zoological station. I learn from the director 

 at the Plymouth Station that some of the animals from deep water, such as Polyzoa, 

 do not expand in their tanks. 



