30 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
twofold; thus, tlie 16-cell stage is a double 8-cell stage, but the gastrula 
stage is never reached. 
The rest of Driesch’s memoir is occupied with a discussion of general 
morphological and setiological questions on which his experiments shed 
light. 
B. INVERTEBBATA. 
Mollusca. 
y. Gastropoda. 
Repair of Shell of Helix aspersa.* — Prof. R. Moynier de Villepoix 
cut away from a young hibernating Helix aspersa several millimetres of 
the peristome and test, and left it under a bell-jar without food. On 
about the third day the denuded part of the mantle was seen to be 
covered with a greyish layer of calcareous matter, and the peristome 
was completely reformed. We see, then, that Helix is not only capable 
of repairing breaches in its shell, but it can, at any rate when it is 
young, completely reform the extreme edge, which then continues to 
grow normally. 
Growth and Structure of Shell in Yelates conoideus and other 
Neritidse-t — Mr. B. B. Woodward describes the remarkable mode of 
shell growth in Velates conoideus ( = Neritina schmideliana , = Nerita 
perversa ), and compares it with other Neritidse. He first discusses a 
series of Neritina species which exhibit stages in the degree of removal 
of the columella and inner walls of the whorls, and in the development 
of the septum. The genus Velates is represented by two species — V. 
conoideus Lamk. and V. equinus Bez. — which occur together in the lower 
and middle Eocene of the Paris basin. In V. equinus the shell growth 
is normal. So far as the myophore is concerned the shell of Velates 
conoideus offers in the growth of the individual a series of conditions 
which in the recent forms find their parallel in distinct species ; in its 
earlier stages the paries and the incipient septum go to form the 
myophore; in the later period the septum alone plays that part, as in 
Nerita crepidularia. “ Put in homely phraseology, the mode of enlarging 
the shell in Velates reminds one of nothing so much as of the Irishman 
who raised his roof by digging out the floor of his cabin.” The very 
hard periostracal layer consists in the main of calcium carbonate with a 
siliceous residue. The crystalline layer is peculiar in the arrangement 
of its plates ; the presence of aragonite in addition to calcite is highly 
probable. 
Slugs of Ireland.^ — Hr. R. F. Scharff has undertaken tho exami- 
nation of the Slugs of Ireland chiefly with a view of solving some of the 
difficulties regarding the distribution of terrestrial animals. Notwith- 
standing that the sea is deadly both to Slugs and their eggs, he finds 
that those of Ireland are closely related to, and are in most cases 
identical with those of the Continent of Europe. Of the thirteen species 
found in Ireland, twelve are identical with those of Great Britain. 
Under each species the author treats of the external characters, the 
* Bull. Soc. Zool. France, xvii. (1892) pp. 30-1. 
t Proc. Zool. Soc., 1892, pp. 528-40 (2 pis.). 
X Sci. Trans. R. Dublin Soc., iv. (1891) pp. 513-58 (2 pis.). 
