December, 191 8, The Irish Naturalist. 165 



ON THE REPRODUCTION OF THE COMMON 

 GARDEN SNAIL, HELIX ASPERSA. 



BY NATHANIEL COLGAN, M.R.I. A. 



There is in existence a considerable body of literature 

 dealing with the life-history and the manners and customs 

 of the Common Garden Snail {Helix aspersa), that air- 

 breathing or pulmonate mollusc so well known to and so 

 little respected by the horticulturist. The animal thrives in 

 my garden in spite of persistent discouragement, and this 

 summer I found it to be uncommonly active in providing 

 for the future supply of the species. In the course of a single 

 day's gardening I came across no less than ten individuals 

 half buried in the soil and laying those clusters of pearly 

 eggs so familiar to us all as common objects of the flower 

 bed. As one of these ten had only begun egg-laying, the 

 cluster having but five eggs, I was tempted to make some 

 observations on the life history of the species in the hope 

 of adding something new to the lore of a somewhat thread- 

 bare subject. 



Selecting for the purpose the snail which had already 

 laid five eggs, I lifted it from its burrow at 5 p.m. on the 

 27th June last, and taking it indoors placed it on a bed of 

 potting mould in a glass petrie-dish, two inches in diameter 

 and one and a half inch in depth, covering the animal with 

 an inch of mould. On examining the dish at i p.m. on the 

 following day the number of eggs was found to be 74, so 

 that 69 had been laid in the course of 20 hours. Placing 

 the snail on the surface of the mould, I was able to watch 

 the process of egg-laying, which continued up to 3 p.m., 

 within which period 9 additional eggs were laid, bringing 

 the total up to 83. The time taken for extrusion, from the 

 first appearance of the egg at the orifice beneath the right 

 upper tentacle until it had been passed downward to the 

 sole of the foot, there to be cemented by mucus to the eggs 

 previously laid, varied from 30 seconds to a minute. A 

 few of the eggs just laid were removed for examination, 

 and the remainder, about 75 in number, were buried in the 



