HELIX. 119 



of observing them during the pairing season, at which 

 time they are in the habit of ascending trees, often 

 (as nearly as I could judge) to a height of from 

 twenty to forty feet, or even higher. The trees 

 usually selected were those growing on the outskirts 

 of woods, in hedgerows by the wayside, or in shady 

 lanes. The beech, ash, and other trees with smooth 

 bark were generally preferred, and although by far 

 the greater number of the molluscs were located on 

 the trunk, others crawled out upon the branches ; 

 aspersa, nemoralis, and hortensis were all of the party, 

 and hybrida, though much less numerously repre- 

 sented, was also present, but I failed to detect a 

 single instance in which it had paired. H. aspersa 

 was less ambitious than its neighbours, and rarely 

 ventured upon an ascent exceeding twenty feet in 

 height. In one locality the trees on either side of a 

 long avenue of beeches were decked with shells. On 

 one of them I counted twenty " happy couples," 

 twelve of which were hortensis, and the rest nemoralis. 

 My object in making this investigation was to deter- 

 mine, if possible, whether matrimonial alliances be- 

 tween these two forms are usual or not, and the result 

 was that among the many hundreds of cases which 

 came under my observation not a single instance of 

 such union occurred the ''black-mouths " invariably 

 paired with " black-mouths," and " white-mouths " 

 with " white-mouths." These observations were not 

 confined to a single locality, but were made in many 

 places some miles apart, and in order to determine 

 with certainty the species of those individuals which 

 were high up in the trees, I used a pair of powerful 



