W. H. Leigh-Sharpe 210 
with or without a constricted neck, about seven times the breadth of a 
normal gill filament. No doubt the hypertrophy was occasioned by the pene¬ 
tration of the free-swimming nauplius larva into the tissues of the gill filament. 
At the proximal bifurcation of the conjunctive tube, deep within the tumour, 
are the faint traces of what appear to be the remains of the cuticle of a dead 
and disintegrated male, the only certain detail of which is the rounded dorsum 
(Fig. 7). If this be proved, the tubes might be definitely called conjugation 
tubes, exhibiting an occurrence wholly unique. During the past four years 
I have examined some hundreds of gurnards without finding Medesicaste, 
neither has that genus been taken at the laboratory of the Marine Biological 
Association, Plymouth, though specially sought at my request. 
Fig. 7. Medesicaste. An enlarged view of the entrance and bifurcation of a conjunctive tube 
(C.T.) in the tumour ( T). $ remains of male animal. 
SUMMARY. 
A tumour among the gill filaments of Trigla gurnardus bears a female 
Medesicaste with the head and neck buried in its apex, and a male Medesi¬ 
caste completely embedded in its base. The two sexes of the parasite are 
connected by a conjugation tube, external to the tumour, down which tube 
the spermatophores presumably pass. The appendages of the copepod are 
described. 
My thanks are due to Michael G. L. Perkins for furnishing me with the 
specimens, and to Miss Edith C. Humphreys for drawings of the specimens and 
preparations which are all mounted unstained in Farrant’s medium. 
