Miscellaneous. Vit 
whereupon a cystic membrane is differentiated. As to what happens 
afterwards and in the interior I am sorry to say that I am unable as 
yet to give any account. Nevertheless it was still possible to see 
that the cavities of the intestines disappear, apparently owing to 
continued multiplication of cells, so that finally the entire contents 
of the cyst are composed of similar cells. I am inclined to believe 
that each of these cells represents a young animal, which, after 
being set free, roves about by aid of its cilia like one of the Ciliata, 
and by further division develops into the adult form; for I observed 
in the same salt-water small unicellular organisms, ciliated on the 
ventral surface only, yet bearing a few cirri in front. These are 
possibly the young forms (larvee).—Zoologischer Anzviger, Xiv. 
Jahrg., no, 367 (13th July, 1891), pp. 230-233. 
On the Growth of the Shell in Helix aspersa. 
By M. Moynizr pe VILirporx. 
We know that the growth of the shell in pulmonate Gastropods 
takes place by the formation, at the edge of the test, of a soft and 
diaphanous zone, which speedily hardens. I have specially studied 
this formation in Heliw aspersa, L. 
The epidermis which gives rise to it is particularly interesting 
owing to the hyaline spherical globules, 10 4 to 12 in diameter, 
which cover its outer surface. Their vature is organic; they persist 
on the oldest shells, and I have reasons for thinking that it is to 
similar formations that we must attribute the markings which are 
to be found on almost all the shells of the genus Heli. 
In animals in course of growth, the thickened border of the mantle 
is always applied against the peristome, and the free edge of the 
epidermis, folded inwards, buries itself, but without any connexion 
with the tissues, in a very narrow cleft which runs round the whole 
circumference of the collar. Immediately behind this cleft, we 
observe beneath the epidermis a white zone bounding the mantle in 
its entire breadth. 
The deposition of calcareous matter takes place on the internal 
face of the epidermis, at some distance from its margin. ‘The origin 
of these products can be understood by examining sagittal sections 
of the collar and mantle. 
The white zone, or bandelet, is a gland composed of flask-shaped 
cells, with very long necks, and granular contents, which bury 
themselves deeply in the subjacent tissue. The action of acetic acid 
and oxalate of ammonia discloses the presence of calcareous matter 
in these cells. 
Behind this bandelet the mantle is clothed with a columnar epi- 
thelium, containing pigment or colourless granulations. 
Immediately in front of the bandelet the epithelium invaginates 
to form the groove in which is lodged the free extremity of the 
epidermis. ‘The bottom of the groove is occupied by an irregular 
plexus of cells, which, in a sagittal section, present the appearance 
of epithelial cells cut obliquely and extending to a greater or less 
distance into the connective tissue. These cells contain transparent 
spherules, presenting all the characters of the globules of the 
epidermis, 
