172 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



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 6i 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 mollusc (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, I 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 mvself, 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). 



