174 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



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 108, 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 like 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 43 per cent., were pearl-bearers — a small 

 proportion compared with ours at Piel. 



■'• 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. 



t Ann. and Mag. Nat. Hist., June, 1903. 



