272 JOURNAL OF CONCHOLOGV, VOL. I5, NO; 9, MAY 1ST, I918. 



opaquely banded shells. A certain percentage of roseozofiaia would 

 almost certainly have appeared in F2, hut at that time I had not 

 arrived at the above explanation of the affair and gave up the 

 experiment. 



It may be interesting to note that at the conclusion of the 

 experiment in June, 1912, six of Fi were alive, all born on the same 

 day in September, 1909, and yet they varied greatly in degree of 

 apparent maturity. Whereas two of them were fully grown perfect 

 specimens, one was but half-grown, two about a third full size, and 

 the sixth was scarcely bigger than when it emerged from the egg two 

 years and nine months earlier although feeding regularly and ap- 

 parently quite healthy until the day the experiment closed. I notice 

 in most of my experiments that such variation in the rate of growth is 

 common. Some shells start growth at once and complete their shell 

 in from fourteen to sixteen months, while otliers take several years to 

 reach maturity. Yet both the slow and the quick growers seem 

 healthy. One is almost tempted to suggest that this diversity might 

 be a provision of nature to prevent all examples of one year's 

 hatching from arriving at perfection in the same breeding season, 

 thus tending to prevent in-breeding. It may be, however, that it is 

 only under artificial conditions that the slow growing specimens 

 would ever attain full growth. 



Experiment No. 5. Helix nemoralis L. 



Two of the roseozonata from Co. Fermanagh used in the last 

 experiment were isolated in March, 19 10. One had five bands, 

 12345, while the other possessed three, 00345. Eggs were laid by 

 one of the snails on the 20th May, 1910, and these hatched out on 

 the 2ist — 23rd June following. The first of the young to reach 

 maturity did so when exactly two years old. Nine specimens of Fi 

 survived until their characteristics were revealed; all were red in 

 colour and all but one were banded. Four were roseozonata; while 

 four had opaque typical bands ; one of the former was 00345 and 

 three were 12345; of the latter two were 00345 and two 12345. Only 

 six completed the lip and of these three roseozonata and one bandless 

 rubella had the white lip of the mother shell. The two opaquely 

 banded shells had normal dark lips. Such a mixed Fi generation is 

 perhaps best explained, as in the last experiment, by the supposition 

 that the mother shell had been fertilized by an opaquely banded 

 example before the former was collected; but in this case by a 

 heterozygous example, thus permitting a percentage of roseozonata to 

 appear in Fr. 



Two families were reared in the F2 generation: "A" from two 

 roseozofiaia, 12345 and 00345 respectively; "B" from the rubella- 



