to-day, as well as its appearance, are not essen- 

 tially different from those prevailing in the past; 

 this is probably due to its unchanged environment. 

 For the cataclysms, the great climatic changes and 

 other natural convulsions which apparently have 

 been potent factors in the evolution of land life, 

 seem never to have exerted any effect on conditions 

 in the deep sea; here, from the most remote period 

 of which there is even plausible proof of life, just 

 as now, it has continued cold, dark, immutable. 

 And so the crinoid, rooted in the oozy bottom, its 

 ghostly flower-like form swaying invisible in the 

 icy unlighted depths, remains the only living relic 

 of that former age, least affected by the passage of 

 time. But to-day it is only a remnant of a once 

 numerous clan. No longer do its beds cover great 

 tracts of the ocean floor; of the two hundred odd 

 genera that formerly thrived, it is doubtful 

 whether more than a dozen now exist. 



But the starfish, serpent-star, and sea-urchin 

 were also on the scene in that early Silurian time, 

 though evidently their numbers, comparatively 

 speaking, were few. It is not unlikely that the sea- 

 cucumber, too, was somewhere around, but no fos- 

 sils betraying its presence previous to the forming 



[88] 



