318 DR. H. LYSTER JAMESON ON 
forming a hemispherical, or sometimes rather more than 
hemispherical pearl-like excrescence, attached to the shell by its 
base. These ‘Culture Pearls” are produced in large numbers, 
and find a ready market for purposes for which “ half-pearls” are 
used. ‘They are now familiar objects in Europe *. 
Text-figure 39 is a section of a Japanese ‘“ Culture Pearl,” 
which I purchased in London, while still attached to the shell, 
and decalcified. 
Text-fig. 39. 

pr col. 
col! ae G7: 
Section through a decalcified Japanese “Culture Pearl” still attached to the shell. 
nu., the artificial “‘ nucleus,” a bead of nacre, the amine of the nacre being 
cut transversely ; pr., prismatic layer; xac., original nacreous lining, which 
existed before the nucleus was introduced ; nac.', more recent nacre, lining the 
shell and extending over the “nucleus” to form the “Culture Pearl,” 
secreted after the introduction of the nucleus; nae.’’, nacreous layers where 
the lining of the shell is carried over the nucleus; col., col.’, repair-substance 
secreted in a zone around the point of contact between nucleus and shell, 
where the deposition of the shell-substance was not controlled by the 
mantle; gr., granular matter, perhaps of foreign origin or of the nature of 
amorphous substance. XX 10. 
The “ nucleus” has been very skilfully introduced, so that there 
is practically no trace of “dirt” between it and the nacreous 
layer with which it is invested, as is so often the case in the 
“ blisters ” which have been produced by naturalists and experi- 
menters from time to time. Moreover, the disturbance of the 
normal functions of the mantle has been so slight that, in the 
* Needless to say, these bodies are not “ Pearls,” biologically speaking, but 
belong to the class of structures to which I have applied the naine “ blisters,” 
familiar on the Australian Fisheries and in the Trade. Various naturalists have 
produced such bodies from time to time. Ihave recently seen some very beautiful 
ones produced in Margaritifera maxima, and I myself produced some presentable 
ones in Margaritifera margaritifera in Papua in 1899-1900. But although 
attempts have been made, and are still being made, to do this on a commercial scale, 
T am not aware that commercial success has yet been achieved anywhere else than 
in Japan; indeed, I think that the combination of circumstances which has led to 
the success of the Japanese enterprise—viz., skill, patience, and intelligence, backed by 
the best scientific advice and supported by cheap labour—has generally been lacking 
in other ventures. J may add that the price that could be obtained for the best of 
these gems is insignificant compared with the value of a real pearl of like size. No 
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