1883.) Pearls and Pearl Fisheries. 731 
of inherited instincts acts as a check to larval nutrition, and tends 
to bring the animal into conditions of quiescence and shelter in 
which its further development may proceed. 
Probably the unfoldment of the mental conditions continues 
even while the animal is active in its larval nutrition. The new 
awakening instincts more and more vigorously oppose the exist- 
ing habits. Eventually the instincts gain precedence, through 
some check to larval nutrition, active life ceases, and the animal 
process of growth is replaced by the vegetative process of organic 
synthesis. At the end of this period oxidation of tissue is re- 
sumed, and the animal starts again into active life, with new 
organs, new powers and new instincts. 
Those insects which pass a period of individual nutritive life in 
the imago state are those which stand highest in the line of evolu- 
tion, and highest of all are the ants and bees, in which larval 
activity and nutrition are largely obliterated, while the imago 
stage of life is long continued. The same may be said of all 
animal tribes. Long life after the reproductive organs appear is a 
sign of a high phase of evolution, and the habits and mental 
strain attained in this stage are superior, since they arise from the 
influence of more complex natural conditions. 
10: 
PEARLS AND PEARL FISHERIES. 
BY W. H. DALL. 
Part II.—MARINE PEARL PRODUCTS. 
uo marine mollusks which chiefly produce the pearl and 
pearl-shell of commerce, are generally known as “ pearl- 
Oysters.” They present little or no resemblance to the oysters 
with which we are familiar, though they are related to them bio- 
logically, They belong to the genera Avicula and Meleagrina of 
Lamarck, and are of three or four species, distributed nearly in 
the same latitude in different parts of the world. The most an- 
cient and famous fisheries are on the coast of Ceylon and in the 
Persian gulf. These were known to Pliny; Ceylon by the name 
Taprobane, and the Bahrein islands of the Persian gulf as the 
Stoides. Beside these the principal fisheries of the present day 
are on the Coromandel coast, India; the Indo-Pacific islands, 
es _ *specially the Sulu group; Margarita island, St. Thomas and other 
