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scarcely be described as free from parasites! He used 70 
mussels; if we take his own figures, one in five, as correct, 
then about 14 of the mussels were infected at the 
beginning of the experiment. We find from his records 
that he only examined 13 of these mussels (2 after 11 
days, 6 after 2 months and 5 after 63 months), and found 
12 of them infected. But it is obvious that that number 
might possibly have been infected from the beginning or 
may have become infected at any time from neighbouring 
mussels. ‘The theory of transference of the parasite from 
one molluse (such as cockle) to another (the mussel) may 
be true, but it is not proved by these experiments. It was 
not shown that the mussels were free from parasites at the 
start, the numbers in the recorded experiments are too 
small to yield definite conclusions, and the observations 
should clearly be repeated using hundreds of cockles and 
of mussels with well-devised control experiments. In 
order to show the necessity for large numbers in this kind 
of work I may add that Mr. Andrew Scott having informed 
me of Dr. Jameson’s observations at Piel, | had some 
samples of these same mussels and cockles sent to the 
Liverpool laboratory where, along with Mr. Walter 
Tattersall, B.Sc., and Mr. J. Pearson, B.Sc., I made (in 
October, 1902), an independent examination of them with 
results that do not altogether agree with Dr. Jameson's. 
We may distinguish between 4 kinds of mussels, 
examined by Jameson and myself, as follows :-— 
(A.) From the beds opposite the Piel Hatchery—* where 
every specimen is abundantly infected . . . - 
and almost every specimen contains pearls 
(Jameson). 
(B.) From the piles of the old pier at Piel—* practically 
without parasites ’’ (Jameson). 
