M. Coste on the Formation of Cells. 377 



C. arabica from one to three inches long ; this peculiarity is at- 

 tempted to be explained by Lamarck and others, who assert that 

 when the animal has formed a complete shell, as it has not the 

 faculty of enlarging its size, it is obliged to quit its shell and 

 form a new one, in the same manner as the Annulosa cast their 

 skins, and by that means the same animal forms many shells ; 

 but I believe there is not the slightest ground for this notion, 

 for these several reasons : 1 . If it happens in this genus, it cer- 

 tainly should do so in several of the other genera, as the Strombi 

 and Pte7'ocerata, where the mouth is fully formed in the small 

 shell, and there is no appearance of varices in the large specimens. 

 2. The nmscular attachment of the shell to the animal is one of 

 the best conchological characters that distinguish this class of 

 animals from the shelly and sandy cases of the Annulosa ; as the 

 Dentalia and Sabellce, where the animals can withdraw themselves 

 at pleasure ; but in the Mollusca I do not think it possible to be 

 done, but by such force as would destroy the individual. 3. There 

 is no analogy between the crust of the Crustacea and Annulosa, 

 and the shells of Mollusca ; so that it is false reasoning to judge 

 of the possibility of one from the other .^^ — Zoological Journal, 

 vol. i. p. 73. 



XLII. — Researches on the Primary Modifications of Organic 

 Matter, and on the Formation of Cells. By M. Coste*. 

 (Part the 1st.) 

 Every one is acquainted with the celebrated experiment of Du- 

 hamel, who, after having bent the summit of a tree towards the 

 earth, inserted the extremities of its branches into the soil, and 

 afterwards turned the trunk so that the roots projected exter- 

 nally, found that these same roots, which had become aerial, shot 

 out branches, whilst the branches which had become terrestrial 

 sent off roots. 



This experiment, the result of which a host of experiments 

 known to agriculturists would have enabled us to foretell, since 

 it was an established fact, that a root which was exposed by any 

 inequality of soil produced a shoot, and that a stem which had 

 been sliced off produced a root, provided that the wound was 

 sheltered from exposure to the air and surrounded with moist 

 earth ; this experiment, I say, furnished so decisive a proof of the 

 identity of the roots and stems, that the objections which were 

 at first made to it have neither prevented our taking advantage 

 of the fertile idea which it reveals, nor arrested the progress of 

 the revolution which the development of its consequences intro- 

 duced into the science of organization. 



* Translated from the Comptes Rendus for October 20, 1845. 

 Ann. ^ Mag, N, Hist. Vol.xyi. 2E 



