SEA-FISHERIES LABORATORY. 123 
NOTE ON A SPOROZOAN (MEROCYSTIS KATHAE, 
‘Ny. GEN. ET sp.) OCCURRING IN THE RENAL 
ORGAN OF THE WHELK. 
By Dr. W. J. Dakin, Assistant Lecturer in Zoology in 
the University of Liverpool. 
Whilst examining and fixing tissues for histological 
purposes, an interesting parasite was observed infecting 
the renal organ of the whelks (Buccinum undatum) which 
have been collected off Port Erin. ‘The parasite is a 
Coccidian. It occurs in enormous quantities, and can be 
detected quite easily with the naked eye in dissections, 
appearing in the form of small white spherules. In 
sections of the renal organ as many as fifteen to twenty 
may appear in the field of view at once (when examining 
with say a 2 in. Leitz objective), showing perhaps three 
or four stages in the life history. The life history has 
been worked out from the examination of a large number 
of sections, and that part of the life cycle occurring in the 
renal.organ of the whelk represents sporogony. ‘The 
earliest stages are small pear-shaped or spherical bodies 
which possess a large nucleus and a very distinct 
nucleolus One or more host cells may be infected and 
the hypertrophied cells extend around the parasite, with 
a large quantity of hypertrophied nuclear material in 
close contact with it. Growth appears to take place until 
a considerable size is attained. After fertilisation, the 
nucleus divides up in an extremely interesting manner. 
By direct division three or four nuclei are formed 
which go to the periphery of the parasite. These divide 
in turn until a number of peripheral nuclei are present. 
Partitions now appear in the cytoplasm until the whole 
is divided into segments, in each of which one or more 
