202 EXPERIMENTAL EVOLUTION LECT. 



Messrs. Irvine and Woodhead. 1 These experiments 

 show that 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 yet able to 

 lay normal eggs, provided with the usual shell, if sul- 

 phate of lime is given to them in their food. It follows 

 that when the hen's organism does not receive carbon- 

 ate of lime as is usually the case, it is able to trans- 

 form sulphate into carbonate. We do not know 

 exactly how things go on in this case, nor even in the 

 normal case. 2 Are carbonate and sulphate of lime trans- 

 formed into phosphate for instance, which is carried 

 under this form to all parts of the organism, and is in 

 the oviduct transformed by nascent carbonic acid the 

 result of the respiration of tissues into carbonate of 

 lime ? In such case the thing would be less surprising 

 than in any other hypothesis ; at all events, whatever 

 the case may be, we have here a very precise* instance 

 of external variation being met by the organism, 

 whether its physiology varies or not. But other 

 animals offer the reverse instance, as Irvine and 



1 R. Irvine and G. Sims Woodhead : On the Secretion of Lime by 

 Animals ) Proc. Roy. Soc. Edin. May 7, 1889, and Secretion of Carbonate 

 of Lime by Animals (Part II.), ibid. 



2 I would refer the reader, for a recent investigation of this matter, to 

 Moynier de Villepoise : Note sur le Mode de Production des Formations 

 calcaires dti Teste des Molhisques. Comptes Rendus Societe de Biologic, 

 1892 



