SEA-FISHERIES LABORATORY. 85 



found, and also contains a description of a new species, 

 Sphaerospora platessce, from the Plaice. Mr. "Woodcock 

 in a second paper describes a very remarkable parasite, 

 Lymjihocystis johnstonei, from the Flounder. 



Other Work. 



Mr. E. D. Laurie, a former student of our Zoological 

 Department at the University, has contributed a short 

 note bearing on the question of the number of eggs that 

 can be produced by an adult plaice. His results for 

 plaice, of about 20 inches in length, from the Irish Sea, 

 agree with those obtained for other seas. Of the three 

 or four hundred thousand large eggs present on the 

 average in such a fish only a comparatively small number 

 are mature at a time, the plaice setting free its ova in 

 successive small batches over an extended spawning 

 period. In stripping a spawning plaice only a certain 

 small proportion of the eggs in the ovary can be extruded. 



The subject of pearl formation in Molluscs, such as 

 mussels and oysters, has been brought into prominence of 

 late years by several investigations and reports both in 

 this country and abroad. As the matter is one of con- 

 siderable public interest and importance, and as there is 

 at present a good deal of misapprehension in connection 

 with it, caused by sensational statements derived from 

 some of the French papers, I have thought it well to give 

 a brief account of the more important recent discoveries 

 and views bearing upon the subject of pearl-formation. 



The relation of sewage disposal to the pollution of 

 our coasts, and to the possible infection of edible shell- 

 fish with pathogenic organisms, has become a matter of 

 national importance. Some previous work done in our 

 laboratory 8 years ago,* drew attention to the matter 



:;: See Report of Ipswich meeting of British Association, Sept., 

 1895, and Lancashire Sea-Fisheries Memoir, No. I., 1899. 



