400 SCIENCE PROGRESS 



familiar with to-day ; and an exactly similar transformation can 

 be followed in an extinct family of South American Ungulates, 

 resulting in the one-toed Thoatherium. Similarly we can trace 

 the ancestry of the camel from the time when it was a graceful 

 antelope-animal with slender feet, until by its migration on to 

 sandy ground it became the splay-toed beast of the present. 



Not only Palaeontology, but likewise Embryology, strongly 

 suggest that Lamarck's theory is true. As our space is limited, 

 we shall select one case to illustrate this. The Hermit Crab 

 differs from other Decapod Crustacea in having a curved 

 abdomen covered only with thin skin, which it protects by 

 thrusting this delicate member into an empty gastropod shell. 

 The appendages of the abdomen are developed only on one 

 side. Now, the young Hermit Crab swims like a shrimp in the 

 sea ; it possesses a straight abdomen with all the appendages 

 developed, and in this it resembles an ordinary shrimp or a 

 lobster. Then it sinks to the bottom, searches for an empty shell, 

 and thrusts the abdomen into it. Now, if all such shells have been 

 previously removed, the search is naturally unsuccessful ; but the 

 Hermit Crab's abdomen becomes curved just the same, though 

 not to the same extent as would have been the case had the 

 shell been forthcoming. 



How are we to explain this metamorphosis on the " muta- 

 tion-theory " or even on the old orthodox Darwinian theory? 

 Are we to assume that, in an ancestral race of shrimps enjoying 

 a free life at the surface of the sea, chance mutations occurred, 

 leading to the formation of a curved asymmetrical abdomen, 

 together with a desire to hide the deformed member in a 

 gastropod shell ? Is it not infinitely more likely that when 

 certain shrimps began to seek their food on the bottom — because 

 of its abundance there — and turned into the forerunners of our 

 crayfish and lobsters, they all began to hide their most vulner- 

 able parts in any crevice they could find, as lobsters do to this 

 day ? Further, that some of them, finding in a gastropod shell 

 a powerful protection, began to thrust their abdomens into these, 

 and so checked growth on one side and promoted it on the other, 

 and that this habit of growth, after many generations, became 

 so ingrained in the constitution that it appeared even before 

 the shell was found. Those who acquired this trick gained an 

 advantage over their allies in that the abdomen was never 

 exposed, since the animal when it had to move carried its pro- 

 tection with it, whereas lobsters could be attacked when they 

 emerged from their retreats. 



But an ounce of fact is worth a ton of theory, and the answer 

 of Weismann and the Mendelians to the supporters of the 

 Lamarckian doctrine has always been that no experimental 

 evidence has been forthcoming to prove the effects of use and 



