M. Coste on the Formation of Cells. 377 
C. arabica from one to three inches long; this peculiarity is at- 
tempted to be explamed 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 Pterocerata, where the mouth is fully formed in the small 
shell, and there is no appearance of varices in the large specimens. 
2. The muscular 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 Sabelle, 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. Cosrn*. 
(Part the Ist.) 
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 aérial, 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. xvi. 
