270 DR. n. LYSTER JAMESON ON 



material. Details of the morphology and histology were 

 then worked out, and the relationship which the larvae bear 

 to pearl-formation was investigated." 



Strange to say, Professor Herdman's Preliminary Report to 

 the Government, dated July 1st, 1902 (13), makes absolutely no 

 reference to the discovery in the previous March of this important 

 aspect of the para,sites of the Pearl-Oyster. 



In the Pi-eliminary Report referred to, Prof. Herdman says 

 (p. 2): 



" Samples of all the oysters obtained by us were examined 

 for parasites and for any diseases or abnormal conditions, and 

 although a considerable number of minute parasites, both 

 Protozoan and Yermean, were found, still that is by no 

 means unusual amongst molluscs, and we do not consider 

 that we saw anything which gave evidence of any epidemic 

 disease or widespread and injurious prevalence of parasites." 



And again in the same Report (p. 4), in his summary of 

 conclusions, the Professor says : 



" A considerable number of parasites, both external and 

 internal, both Protozoan and Yermean,' were met with, but 

 that is not unusual in molluscs, and toe do not regard it as 

 affecting seriously the oyster j^opidation." (The italics are 

 mine.) 



In view of the last three quotations, if it were not for the very 

 definite assertions in Part II. p. vi, and Part Y. p. 6, of Professor 

 Herdman's full report, quoted above, I should be almost inclined 

 to think that, while the Cestode lai'vje were no doubt discovered 

 " in association with pearls " during Professor Herdman's cruise, 

 the Cestode theory of Pearl-formation might have been evolved 

 after Professor Herdman's return to England, and after the above- 

 mentioned pi'eliminary report had been submitted. In that case 

 Mr. Hornell might well have been misled by the false analogy of 

 the case of the Trematode origin of peai-ls in Mytilas, which was 

 dealt with at length in my paper (25). This paper appeared 

 in August 1902 ; that is to say shortly after the Professor's pre- 

 liminary report of July 1st, 1902, containing no reference to the 

 Cestode theory, was submitted. The view that my paper might 

 have misled Mr. Hornell and Professor Herdman would also derive 

 support from the fact that the real point of my paper had appa,rently 

 been missed, viz. that it is not the presence of any parasite, but 

 the specific stimidation of a pa7^tiGidar hind of parasite that 

 causes the growth of the pearl-sac. I consider this point is by far 

 the most important contribution I have so far made to the svibject, 

 and I believe it will be the basis upon which a rational system of 

 artificial pearl-production will ultimately be built. 



The first announcement of Prof. Herdman's theory of Pearl- 

 formation seems to liaA^e been made at a lecture delivered before 

 the Royal Institution on March 27th, 1903, an abstract of which 

 appeared in ' Nature ' for April 30th of the same year (14). 



