PRE-DETERMINATION IN NATURE 335 



as we see in the modern Limulus; and each of these ocelli must 

 have been a perfect photographic camera, and more than this, 

 since absolutely automatic, and probably having the power to 

 represent colour as well as light and shade. We know also, 

 from the recent experiments of an Austrian physiologist on the 

 eyes of insects, that such compound eyes are so constructed 

 as to present a single picture, just as we can see the whole 

 landscape in looking through the many little panes of a cottage 

 window. In our own time the king-crab and lobster no doubt 

 see just as their predecessors did millions of years ago, and with 

 precisely similar instruments. 



But the eyes of the modern Crustaceans have to compete 

 with eyes of a dissimilar type, constructed on the same general 

 optical principles, but quite different in detail. These are the 

 simple or single eyes of the cuttlefishes and the true fishes. 

 The same rivalry existed in the oldest seas, when the com- 

 petition of Crustaceans and cuttles was just as keen as now. 

 Though the eyes of the latter have not been preserved, or at 

 least have not yet been found, we have a right to infer that the 

 cuttles of the Cambrian and Silurian seas must have been able 

 to see as well as their Crustacean foes and competitors. If so, 

 the other type of eye must have been perfected for aquatic 

 vision as early as the compound type. In any case we know 

 that a little later, in the Carboniferous period, we have evidence 

 that the eyes of fishes conformed to those of their modern suc- 

 cessors. I have myself described l a carboniferous fish (Palcz- 

 oniscus) from the bituminous shales of Albert County, New 

 Brunswick, in which the hard globular lens of the eye had been 

 sufficiently firm and durable to retain its form, and to be re- 

 placed by calcite, showing even that like the lens of the eye of 

 a modern fish it had been constructed of concentric laminae. 

 In the Carboniferous period also, both types of eye, the com- 

 pound and the single, experienced the further modifications 

 1 Canadian Naturalist, 



