60 THE WHENCE AND THE WHITHER OF MAN 



The clam is so completely protected by his shell and 

 the mud that he has little to fear from enemies. They 

 have increased and multiplied and filled the mud. 

 " Requiescat in pace." 



But zoology has its tragedies as well as human 

 history. Let us turn to the development of a third 

 molluscan line terminating in the cuttle-fishes. The an- 

 cestors of these cephalopods, although still possessed 

 of a shell and a high visceral hump, regained the swim- 

 ming life. First, apparently, by means of fins, and then 

 by a simple but very effective use of a current of water, 

 they acquired an often rapid locomotion. The high- 

 est forms gave up the purely defensive campaign, de- 

 veloped a powerful beak, led a life like that of the old 

 Norse pirates, and were for a time the rulers and ter- 

 rors of the sea. With their more rapid locomotion 

 the supra-oesophageal ganglion reached a higher de- 

 gree of development, and it was served by sense- 

 organs of great efficiency. They reduced the external 

 shell, and succeeded, in the highest forms, of almost rid- 

 ding themselves of this burden and encumbrance. 

 Traces of it remain in the squids, but transformed into 

 an internal quill-like, supporting, not defensive, skele- 

 ton. They have retraced the downward steps of their 

 ancestors as far as they could. And the high develop- 

 ment of their supra-oesophageal ganglion and sense- 

 organs, and their powerful jaws and arms, or tentacles, 

 show to what good purpose they have struggled. But 

 the struggle was in vain, as far as the supremacy of 

 the animal kingdom was concerned. Their ancestors 

 had taken a course which rendered it impossible for 

 their descendants to reach the goal. Their progress 

 became ever slower. They were entirely and hope- 



