~ 
oO 
found, and also contains a description of a new species, 
Sphaerospora platesse, from the Plaice. Mr. Woodcock 
in a second paper describes a very remarkable parasite, 
Lymphocystis johustonei, from the Flounder. 
Oiinh ene | Wrormke. 
Mr. R. 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, L., 1899. 
