The eggs of Helix are laid separately in the earth, each contained in a calcified shell; those of Limax are also separate, but the shell is gelatinous.
Pallas in 1778, who took them to be slugs and described them under the name Limax lanceolatus.
The Romans are credited with having purposely introduced the edible snail (Helix pomatia) into England, and the common garden snail and slugs (Helix aspersa, Limax agrestis and Anion hortensis) have been unwittingly established in New Zealand.
In other slugs, namely, Limax and Anion, the shell-sac remains permanently closed over the shell-plate, which in the latter genus consists of a granular mass of carbonate of lime.
In Helix and Limax the osphradium has not been described, and possibly its discovery might clear up the doubts which have been raised as to the nature of the mantle-chamber of those genera.
Areas are found on the foot of the embryo Pulmonate Limax and on the yolk-sac (distended foot-surface) of the Cephalopod Loligo.