A *' Living FossiF^ 225 



cause of Its disappearance is as obscure as that of its 

 origin. 



Although the typical trilobite has ceased to exist, 

 It has living to-day a relative in the horseshoe crab 

 {Limuhis polyphemus) ^ the sole surviving descendant 

 of an otherwise extinct group of animals. The life his- 

 tory of LImulus is as interesting as it is simple; for in 

 the development of this ancient creature is to be found 

 one of the most beautiful illustrations of that great 

 natural principle which seems to prevail to the effect 

 that the ancestral forms are recapitulated in the embry- 

 onic and larval stages of the individual. 



The horseshoe crab is found along the whole At- 

 lantic coast from Maine to Yucatan. Although far 

 less numerous than even a generation ago, it is still 

 common enough to be one of the most familiar animals 

 of the seashore. Considering for a moment the in- 

 creasing scarcity of this creature, it may be stated that 

 in recent years mankind has become more and more 

 aware of its edible properties and of its value as a soil 

 fertilizer. This has resulted in a wholesale and unin- 

 telligent slaughter. Naturalists have recorded that as 

 late as the year 1856 more than a million horseshoe 

 crabs could be seen to come ashore and lay their eggs 

 within a single mile along certain sections of the East- 

 ern coast. That this abundance nowhere near exists 

 to-day Is ample testimony that their future Is very In- 

 secure, and unless some measures are taken to preserve 

 them, they will at the present rate of decrease prac- 

 tically be exterminated within the time of men now 

 living. 



Limulus lives on sandy and muddy shores below the 



