105 

 ON THE GROWTH OF SOME LAND SHELLS. 



BY H. R. BOLTON^ ESQ. 



The last two years I have been payiiig some attention to the growth of a few 

 of our common Land Shells, from the time of their first appearance after leaving 

 the egg, until their arrival at maturity. I was led to this by seeing a table 

 formed from M. Bouchard's observations, in an edition of "Turton's Manual 

 of Land and Fresh- water Shells," published in 1840, page 306, wherein it is 

 stated of the Zoned Snail, (Melis virgata,) that the time thus occupied is 

 from eighteen to twenty-four months. 



Whether climate, soil, or locality may create a difference, I am unable 

 to say; but this does not agree with the habits of this species of Helix in 

 the neighbourhood of Plymouth I have reason to suppose, from observation, 

 that the entire life of the animal is disposed of in twelve months; that it 

 is an annual; and that it seldom outlives the winter. About September we 

 find the adult animals in colonies of thousands. Towards the latter part of 

 October they begin to disappear, and by December nearly all are gone into 

 the earth, where they secrete themselves under tufts, roots of grass, etc., 

 and they there deposit their eggs: this act being performed, the animal dies. 

 On the returning warmth of spring the eggs are hatched; but the young are 

 not seen until about midsummer. They did not make their appearance this 

 season until the showers of rain which fell in the beginning of July. They 

 then came forth in abundance. I observed hundi-eds in a minute state, the 

 apex formed, and small whorls just indicated. In ten days after they had 

 grown to a third part of their natural size, in twenty days two-thirds, and 

 from thirty to thirty-five days they had attained a state of perfect maturity. 



Another shell, common in this neighboiu'hood, I find to be also an annual 

 — the Twist Shell, (Bulimus acutiis;) but its growth is very different, and 

 far less rapid than the above. The young of this Helix make their first 

 appearance in March, with the apex and one or two small whorls formed, 

 and although there are myriads of them, not a single mature shell is to be 

 seen or found among them, nor at any other period during their growth. 

 In April they are enlarged by another whorl, ,in May by a fourth, by June 

 they have five whorls, in July they have increased to six or seven, and 

 about August arrive at full maturity. 



They remain on the surface until November, when they bury themselves in 

 the sandy soil which they inhabit, creeping under the roots of herbage, tufts 

 of grass, etc., where they deposit their eggs, and are no more seen alive. 

 A few dead shells may be occasionally found washed by the rain, and drifted 

 from the sand. The same occurs in the Helix virgata, whose dead shells 

 may be frequently seen on the surface of the turf. 



16, Alfred-Street, Plymouth, Novemher 12tJi., 1851. 



VOL. II, 



