Trans. N. V. Ac. Set. 54 Jan. 21, 



rudimentary and imperfect organs of this sort. This is one of the 

 many mysteries of the geological record, that the successive steps in 

 the development of means of offence and defence should be so rarely 

 found, and it is one of the difficulties of Darwinism as the theory o 

 the universe. Incomplete organs of offence and defence would often 

 be inoperative and useless, like a bridge which is of no value what- 

 ever if it only partly crosses a stream. The horns of a bull can 

 be of little service, till they project from the head and are well pro- 

 gressed on the road to maturity. 



In geological history there is recorded a well-marked progress in 

 the character and efficiency of the devices for offence and defence. 

 Taking for example the placoderms of the Devonian for our starting- 

 point, as these are the earliest well known fishes, we find them en- 

 cased in armor which would bid defiance to all offensive weap- 

 ons ; but it was so much of a load to carry that they must have been 

 inactive and unenterprising animals. In the Carboniferous age the 

 placoderms had given place to the scaled ganoids and sharks, which 

 were less protected by armor but more active. These continued 

 their reign till the middle of the Cretaceous, when the teliosts, like 

 the trout and salmon, took possession of the waters. These latter are 

 but moderately provided with means of offence, and their thin 

 and flexible scales afford little protection against attack ; and yet 

 they have practically taken possession of all rivers, lakes, and bays, 

 and far outnumber other fishes in the open sea. By what means 

 these small and light armed troops gained so complete a victory over 

 their armor-clad predecessors, we can only conjecture ; but, it is prob- 

 able, because they possessed greater intelligence and activity, their 

 superior nerve-power being more than an equivalent for the passive 

 protection of spines and bony plates. In the competition for the food 

 supply which has apparently been the chief struggle of life, the quick- 

 witted and quick-moving teliosts would circle around their slower 

 rivals, and, by devouring their food, create a desert in which they 

 starved. 



Similar facts may be observed in the history of the changing fash- 

 ions in regard to offensive weapons and means of defence among 

 animals, including Man. A large number of the Carboniferous sharks 

 were provided with formidable spines ; now only a few sharks and 

 the chime-eras retain their spines, but these greatly diminished in 

 size, and more ornamental than useful. So, a century ago, every 

 gentleman wore a small sword, which he was only too ready to use. 

 Where this fashion was general it became universal, for an unarmed 

 man, in a crowd w-ho carried arms, was quite at their mercy. 



In the middle ages all warriors were clad with mail : but this, to be 



