418 THE CANADIAN NATURALIST. [i ol. IX. 



organs as subserve the function could be produced by any pro- 

 cess of evolution. 



So far as appears there are many aberrant or peculiar organs 

 in the animal economy that cannot be accounted for by evolution, 

 because the terms of any conceivable theory of evolution cannot 

 apply. Let us take but one example — the ink bag of the oc- 

 topus. It is vs^ell known that all the dibranchiate cephalopods, 

 when threatened by danger, eject into the surrounding water a 

 dense, dark liquid that forms an opaque cloud to cover their 

 escape. This dark brown or black liquid is secreted abundantly 

 by a somewhat large sac-like gland — the ink bag. Exteriorly 

 the ink bag is pear-shaped, and has a pearly or silvery lustre. 

 Within, its walls are cavernous, and pour the secretion into a 

 central cavity, from which a tube conveys it to the funnel of , the 

 animal. When alarmed the animal forcibly expels water from 

 its funnel. By the reaction of this water it is driven rapidly 

 backward. At the same time the contents of the ink bag are 

 shed into the escaping jet of water, so that the very act by which 

 the animal escapes, aids in the formation of the cloud that covers 

 its escape. 



This function of darkening the water by a dense coloured se- 

 cretion is one which is not found in protozoan life. It exists 

 nowhere in the animal world in a rudimentary condition. The 

 geological record shows that just when, in the Jurassic seas, the 

 armored cephalopods had reached their culmination, the belem- 

 nites and teuthidae suddenly appeared in considerable numbers, 

 both of individuals and species, all destitute of the protection of 

 an external shell, but all fully provided with the unique means 

 of defence described above. But geology gives no record of any 

 preceding form of life that had a similar though less perfectly 

 developed defence. Yet, if such form of life had existed, it 

 would surely have left some record of its existence. If in no 

 other way, its indestructible ink would, in some cases at leasts 

 have remained to witness for it. There is no evidence then of 

 the evolution of the ink bag of the cuttle fish. It appears at 

 once fully developed. Nor is it possible to conceive its evolution. 

 A cloud of ink insufficient in quantity or pale and translucent in 

 colour, so far from being of utility, would have been a serious 

 disadvantage to the ink spiller. It could not have served for 

 concealment; it would have been a means of betrayal only. The 

 evolution of an ink bag bv selection under the struggle for exist- 



