334 PRE-DETERMINATION IN NATURE 



but the general principles and main structures all stand. I 

 was much struck with this recently in studying a remarkable 

 specimen now in the National Museum at Washington. It is 

 a large species of Asaphus; the same genus which gave to the 

 late Mr. Billings the limbs of a Trilobite, the first ever dcr 

 scribed ; but in the Washington specimen they are remarkably 

 perfect. Each limb presents a series of joints resembling 

 those of the tarsus of an insect, each joint being of conical 

 form with the narrow proximal end articulated to the enlarged 

 distal end of the previous one, so as to give great facility of 

 movement and accommodation for delicate muscular bands. 

 This tells us of muscular fibre and tendon fitted for flexing 

 and extending these numerous joints, of motor nerves to work 

 that marvellous contractile power of the striated muscle, 

 whose mode of action is still an insoluble mystery, yet one 

 practically solved in the remote Cambrian age for the benefit 

 of these humble inhabitants of the sea. If we could imagine 

 that the inventive power to perfect such machinery was pre- 

 sent in the brains of these old Crustaceans or Arachnidans, we 

 might wish that some of them had survived to instruct us in 

 matters which bafile our research. 



It is long since the compound eyes of these Trilobites, as 

 illustrated by Burmeister, gave Buckland the opportunity to 

 infer that the laws of light and of vision were the same from 

 the first as now. But what does this imply ? Not only that 

 the light of the sun penetrating to the depths of the Cambrian 

 sea, was regulated by the same laws as to-day, but that a series 

 of cameras was perfected to receive the light as reflected from 

 objects, to picture the appearance of these objects on a retinal 

 screen as sensitive as the film of the photographer, and thereby 

 to produce true perceptions of vision in the sensorium of these 

 ancient animals. I have before me a fragment of the eye of a 

 Trilobite {Phacops)^ in which may be. seen the little radiating 

 tubes provided for the several ocelli of the compound eye, just 



