112 Miscellaneous. 
There is thus formed in the connective tissue a series of regular 
glandular sacs, adhering one to another. On teasing out the tissues 
of the living animal it is seen that these gland-cells attain consider- 
able dimensions, and that the globules are formed at the expense of 
their granular protoplasm. The globules originate and grow in 
vacuoles, which become successively hollowed out in the protoplasmic 
mass, so that finally the cells are nothing more than transparent 
masses formed by an agglomeration of little delicate-walled alveoli 
enclosing the globules. The latter, on being set free, probably by 
simple rupture, emerge at the bottom of the groove, where they 
attach themselves to the fine organic membrane secreted by the 
epithelium. 
The calcareous and mucous glands are absent, as stated by 
Leydig*, in all the parts covered by the shell, and I was able to 
prove that the calcareous glands of the collar, conformably to the 
opinion of Semper, do not contribute in any way to the formation 
of the test. 
The only elements which take part in the production of the 
latter are, commencing from in front:—(1) The pallial groove, 
where is formed the epidermis with the glandular sacs, which pro- 
duce the globules, and the existence and function of which I believe 
I am the first to describe; (2) the bandelet, or pallial gland, on 
which appears to devolve "the secretion of the calcareous matter ; 
(3) the pallial epithelium following the bandelet, which provides 
the shell with its pigment and completes its calcification by the 
deposition of organo-calcareous layers, homologous to the layers of 
nacre in the Pelecypods. 
I determined, moreover, that, when the animal has attained its 
full size, the bandelet and the glands with globules have completely 
disappeared. 
It is only the epithelium of the mantle and of the pulmonary sac 
which retains its activity, for the purpose of contributing to the 
internal thickening of the test, and also of replacing the loss of 
portions of it, as is shown by the following experiment, which 
indicates the rapidity and activity of the secretion. 
If we lay bare a portion of the surface of the pulmonary sac, 
by removing a fragment of the shell, it is possible even at the end 
of an hour and a half to two hours to detach an extremely delicate 
organic membrane, covering the whole surface, and strewn with 
rhombohedral and radiating crystals of carbonate of lime. If 
allowed to remain, this membrane thickens very rapidly, and finally 
closes up the opening with a solid calcareous wall. 
In no case (contrary to the statement of C. Picard Tt) does the 
mucus produced by the collar or the mouth take part in this pro- 
cess of reparation. 
As regards the activity of the pallial epithelium, it is such that, 
during two consecutive months, I was able to observe animals, 
which were deprived of food, reproducing every day the organo- 
calcareous membrane which I removed every morning.— Comptes 
Rendus, tome exiii. no. 7 (August 17, 1891), pp. 317-319. 
* Leydig, ‘ Die Hautdecke und Schale der Gastropoden.’ 
+ Dr. Om Picard, ‘Hist. des Moll. terr, et fluv. qui vivent dans le 
département de la ‘Somme,’ 1840, 
