Sinistral Helix nemoralis at BundoranAuthor(s): A. E. Boycott and Captain C. DiverSource: The Irish Naturalists' Journal, Vol. 1, No. 2 (Nov., 1925), pp. 24-25Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25531143 .

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24 The Irish Naturalists' Journal.. [Vol. 1.

and aboufc the middle of July a fourth. Two of these foundations,

though persevered in for some time, came to nothing, and in one

instance the cause of the failure was evidently the failing health and exhaustion of one of the building birds.

The two other pairs completed their nests (F- and G.), whose record for the season was, however, very poor. In G?the nest

begun June 21st, which was not finished until August 3th?a brood of one young bird, which took its first flight on September 15th, was the fruit of the season's activity. In F?the nest begun

May 12th, finished May 30th?no young ever appeared, and the nest on examination was found to contain a dead female, sitting on two partly incubated eggs. As a dead bird had again been found in the yard this year (May 30th), this makes the fourth instance of a serious nesting-season mortality to which Martins are evidently subject.

On the other hand the four old nests each safely reared two

broods, though they were all small broods this year, the largest not exceeding three. The usual amount of ledge-making was also carried on, by birds presumably below the three-year-old age.

In the following year (1900), though the work of my colony went on as usual, a second colony, probably an off-shoot of the

Ballyhyland one, established itself in a farmyard less than a mile away, so that a continuous family record ceased to be possible. I believe, however, that this eight years' record is of some in

terest, going to show, among other things, that it is not the

practice of House-Martins to begin breeding before, ihey are three

years old, and that the numbers which return to us in spring, though only

a minority of them may make nests, are not?unless

after a stormy passage?very much below the strength of those that leave us in autumn.

SINISTRAL HELIX NEMORALIS AT BUNDORAN. By Professor A. E. Boycott F.B.S., M.D., and

Captain C. Diver, M.A.

A great many species of snails in which the shell is normally twisted in a right-handed spiral exhibit an occasional specimen with a left-handed turn: such examples have been found probably in the majority of species of which large numbers have been care

fully looked at. As Mr. Welch points out in the last number, a

great many sinistral H. nemoralis have been found at Bundoran. This might be due either to the existence there of a race consisting wholly or partly of sinistrals or to the fact that vast numbers are handled in the industry of necklace making. We made a short expedition to Bundoran in September, 1924, to investigate the

matter further and in the hope that we might find some live sinistrals to breed from. A study was also made of the prevalence of the different colour and band forms in different parts of the Finner dunes and of their association with one another. In all 19,000 live specimens were collected, cleaned and classified: all

were dextral, At least as many more were looked over more

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November, 1925.] 25

casually without finding a sinistral shell, so that we may conclude that at the present time there is no "race" of sinistral nemoralis in that locality in the sense that the population contains an ap

preciable number of such individuals;?comparable, for example, to the race of Limncea peregra in the pond at Leeds which has about 3 or 4 per cent, of sinistrals. The shells used for the neck laces are the dead shells which collect in prodigious numbers in the

" blow outs." Some of these are recent, but the majority are

apparently derived from ancient specimens embedded in the older

sandhills; when these are blown to pieces by the wind the nemoralis are as it were sieved out and strewn over the floor in an ideal way for the conchologist. On one small area about the size of a tennis lawn we estimated that there were about 200.000 shells. A morning was spent in going systematically through 8,000 of these; the 6,021st was a sinistral, and a great many

more were looked at without counting them and without finding another. Prom this we conclude that the large number oi sinistral shells which have been found at Bundoran is probably due to the enormous numbers which have been examined, though the possibility cannot be excluded that there used to live there a race with 1 sinistral in 5,000 or 10,000 or some such

frequency. The enquiry made one realise how difficult it is to examine

really large numbers of any species. Man is the best known animal and human abnormalities which occur once in 10.000

people are well-known and their inheritance has been in some cases ascertained; abnormalities which affect one person in a

million can be seen fairly frequently owing to the intensive survey of human beings which is always going on. It seems impossible that our knowledge of wild animals should be equally complete, though perseverance mid co-operation may effect something.

Few conchologists probably realise how many 20,000 snails are:

yet it is a trivial sample of such a population as lives on the Bundoran sand-hills.

Curiously enough, we did find a single live young sinistral nemoralis in a small colony on the roadside outside Ballyshannon some miles from the sand hills.

Finally, we should like to suggest that anyone who has access to a place where the species is common might undertake a

systematic search to determine the proportion of sinistrals in the

population, aiming at numbers of the order of 100,000 or half a million. The authors would be glad if anyone undertaking such a survey would communicate with them, and they would willingly give any assistance possible.

17 Loom Lane, Badlett, Herts.

" The study of Natural History has a peculiarly elevating effect upon

character, and, in these days, when education consists more of cramming than of culture, it is well to encourage a pursuit which ia healthy both to the body and to the mind." F. Balfoi / Browne in preface of "Concerning

the Habits of Iflsects.'' (See ,p. 38).

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