3 2o THE POPULAR SCIENCE MONTHLY 



the formation of the crab-shell. This, however, is not the case in the 

 formation of the egg-shell of birds. To quote de Varigny, page 202: 



When laying hens are deprived of carbonate of lime by being shut into a 

 room lined throughout with wood, without sand or soil, they are able to lay 

 normal eggs, provided with the usual shell, if sulphate of lime is given them 

 in their food. It follows that when the hen's organism does not receive car- 

 bonate of lime, as is usually the case, it is able to transform sulphate into 

 carbonate. 



De Varigny then says that other animals offer the reverse instance 

 and alludes to the facts about the crab-shell, but does not see that this 

 apparent contradiction is in any way associated with the great differ- 

 ences in organic complexity between the two animals, or that similar 

 environmental changes have here produced a marked difference in the 

 end product in the case of the lower creature and nothing in the case 

 of the higher. 



But these experiments are overshowed, and the great plasticity of 

 this group of invertebrates is chiefly shown by the powers of regenera- 

 tion which they possess. Experiments showing remarkable regenerative 

 powers of the claws of lobsters, shrimps, crabs, crayfish, etc., are well 

 known, and may be found described at length in any text-book dealing 

 with the subject. In this respect they stand, according to Przibram, 

 about on a level with the mollusks. 



Insects 



As soon as our review brings us to this highly differentiated group 

 of invertebrates we see for the first time the fact that remarkable modi- 

 fications are now chiefly associated with changes in the integument, 

 especially changes of pigmentation. Profound modifications of a struc- 

 tural sort, and marked differences in body size are no longer met with. 



We find, however, that changes in the surrounding temperature, 

 and changes in food, affect the length of time occupied in the different 

 stages of development of Lepidoptera; but in the end the result appears 

 to be the same as under normal conditions. Morgan says : " The moth 

 is identical with the normal," and at the end of his description of these 

 experiments quotes the following : " What the insect gains in the larval 

 stage it loses in the pupa stage." 16 



Some change in the size of the wings of the adult imago is another 

 modification of an unimportant sort, and noted by Standfuss as a result 

 of raising and lowering the external temperature during the larval 

 period. 



For example, a pair of A. fasciata, of which the wings measured, respect- 

 ively, 46 and 48 mm. across, produced three specimens measuring only 36 to 

 39 mm., when the larval stage was reduced to 68 to 87 days, and the pupal to 



16 " Experimental Zool.," p. 314. 



