Selection of ]\v\'\k noinoralis hi/ the Sotig- I /iriis/i. .'t27 



taken from A, iioiio tVoiu H, tlnor from (\ live from 1), and 

 tive from K, although the two latter ^ronps were not pnt 

 ont until four days after the others. Unlortnnattly it was 

 not jiossihU' to make U)nj;er observations, hut, as far as tliey 

 p:<\ they sufjf^est : (a) that the thrushes, so far frotn ehoosing 

 the lightly handed shells, actually preferred the four-handed 

 variety, although this was not the most numerous form 

 provided ; (/>») that thrushes niayhreak snails which for some 

 reason they do not eat; (r) that there is a tendency for 

 snails to he taken from the more cx|)Osed places. If the 

 distributi{)n of //. w<';«(//V7//5 at Quy Fen obtains elsewhere, 

 the latter factor alone might account for the large proportion 

 of unhanded shells at the " anvils '' recorded by Mr. Trueman. 



A second series of observations was carried out near 

 Cambridge round an artilieial piece of water. The place, 

 which is (jf about !• acres area and surrounded by fields, is 

 lush-grass thickly interspersed with cypress, |)rivet, and 

 l)ranible-bushes. In the season in question it was inhabited 

 by one pair of thrushes, who reared two broods there. 

 Collections were made at intervals, with tlic results set out 

 in Table II. On July .'31st anvil I. only was taken. On 

 August l.'ith it was emptied again, and II., III., and IV. 

 were found. Therefore the numbers foraiivil I. on this date 

 re|)resent a proportion of the thrushes' takings for a fort- 

 night. The large pro|)ortion of Helicella cantiana found 

 broken may possibly be accounted for by the dry weather 

 that prevailed at the time. In August attempts were niade 

 to form a control collection, but ouing to the drought they 

 were unsuccessful, and fun her opportunity did not arise 

 until October l:jth-.'Jlst, when, after long search, living 

 (mostly immature) specimens were found, as recorded ou 

 Table III. 



\Nhile the control coUcetion is thus so small, judgment 

 must be sus|)CMd«'d ; but so far there seems no ground for 

 suj)posing that the banded shells were taken less fretpientlv 

 than ihe unhanded, nor thai, when taken, they were not 

 eaten. After my observaticjus on the tethered snails, I was 

 prepared to find that the heavily banded shells were dis- 

 tasteful to the birds ; but the later observations dispose of 

 this idea, and as these anvils were made in the summer, when 

 insect food was plentifid, it could hardly be that hunger 

 drove the birds to eat unpalatalde food. 



I shoidd like here to express my indebtedness to Mr. II. H. 

 Blind ley, .M..\., of St. John's College, for his assistance in 

 forming these collections and for much helpful criticism 

 and advice. 



