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cockle contains the earlier stage of the parasite, and passes 
it on to the mussel. 
A couple of weeks later, at the end of October, 1902, 
Mr. Scott and Mr. Johnstone being together at Piel, 
examined some further samples with the following results :— 
(A.) Examined 61, got 390 pearls and 191 parasites. 
(B.) Examined 103, got 100 pearls and 61 parasites.* 
(D.) Examined 53, got 161 pearls and 66 parasites. 
(Roosebeck Scar mussels could not be got at the time). 
The most noteworthy difference between these results 
and mine are in the case of the parasites in (A.), where Mr. 
Scott found about seven times as many as we did. The 
sample of (B.), in this case also, it will be noticed, is by no 
means free from infection. Since then Mr. Scott has ex- 
amined a few more samples with slightly different results : 
but I do not wish to attach too much weight to any of 
these figures. The point I desire to make is that in 
working with these comparatively small samples each 
examination gives a different result, and that consequently 
it is necessary that some one lke Mr. Scott, living on the 
spot, with abundance of material at hand, and with tanks for 
experiments under constant observation, should make a 
comprehensive investigation of some hundreds of each kind 
of mussel and cockle, in order to clear up the distribution 
of pearls and parasites, and settle the question of infection. 
Prof. McIntosh + describes the examination of 700 
mussels from near St. Andrews, and finds that 300 in 
all, or nearly 48 per cent., were pearl-bearers—a small 
proportion compared with ours at Piel. 
}Ann. and Mag. Nat. Hist., June, 1903. 
*As this was going to press Mr. Johnstone informed me that 
before he made the examination referred to a gale had washed away 
some of the piles of the old pier, and that his sample of (B) was 
obtained from a lower level than Jameson’s, and so may have 
“ contained more parasites. 
