318 The N.Z. Journal of Science and Technology. [Sept. 
The Economics of Trochus niloticus, by Charles Hedley. Australian 
Zoologist, vol. 1, pt. 4, pp. 69-73, plates v-vi. Sydney, N.S.W., 1917. 
Mother-of-pearl was at one time obtained chiefly from the pearl-oyster 
(Meleagrina margaritifera L.), which is not a true oyster, but a member of 
the Aviculidae. The demand having greatly increased in recent years, 
new sources of supply have come into use, one of the most important of 
which is the shell Trochus niloticus L., which ranges from Ceylon to Samoa, 
the Loo Choo Islands, and the tropical coasts of Australia. Trochus-fishing 
is carried out on the Great Barrier Reef, and in 1916 the export was 950 tons 
of shell, valued at £23,000— i.e., slightly over £20 per ton. There are also 
large fisheries in New Guinea, the Solomon Islands, and Fiji. 
The paper under notice was written as a report from the Special Com¬ 
mittee on Marine Biological Economics of Tropical Australia, appointed 
by the Commonwealth Advisory Committee of Science and Industry. 
Mr. Hedley discusses briefly the nomenclature and geographical range, 
devotes considerable space to the description of the shell, and details 
the methods of fishing and the regulations under which it is conducted. 
The beautiful plates accompanying the paper show clearly the method 
of cutting the buttons from the shell. 
While Trochus niloticus does not occur so far south as New Zealand, 
and our representatives of the Trochidae are too small and thin for economic 
purposes, it is possible that another family, the Turbinidae, might furnish 
some suitable material; one member in particular, Astraea sulcata (Martyn), 
is large, solid, and has a white nacre. Turbo granosus (Martyn) is also solid 
and white, though smaller. Then, too, the common green paua ( Haliotis 
iris Martyn) would probably be suitable for some classes of buttons, or 
for other ornamental work. M. K. M. 
CORRESPONDENCE. 
Proposed Introduction of Animals and Plants. 
Sir, —The paper by Mr. H. W. Simmonds, F.E.S., on the subject of the 
acclimatization of animals in New Zealand, which was published in the 
May number of this Journal, is one that requires careful consideration 
from more than one standpoint. 
From a natural-history point of view New Zealand has probably suffered 
more than most countries from the well-meant but uninstructed efforts 
of acclimatization enthusiasts. When one considers the numbers of exotic 
animals (to say nothing of plants) that have been deliberately introduced 
into this country during the past hundred and fifty years, it is really 
surprising that any of its indigenous animal inhabitants have survived. 
The average person who advocates acclimatization experiments appears 
to think that foreign animals and plants can be introduced into a country 
in much the same way as plums can be introduced into a pudding. He 
has not the slightest conception of the highly complex relations and delicate 
balance that exist between the living productions of a given region, and 
he consequently imagines that when he has succeeded in establishing his 
thrush, his frog, and his weasel all that remains for him to do is to sit 
down complacently and pose as a benefactor of his country. 
I regret to think that Mr. Simmonds appears to believe in the plum¬ 
pudding theory of the relations between organic beings. While he is 
