438 
parasite was situated near the middle of the swelling, almost filling 
up the proximal half of a cavity. This cavity begins in the centre of 
the truncate end as a rather narrow duct (fig. 2), and widens proxi- 
mally so that its diameter a little before the proximal end is nearly 
twice as long that of the terminal opening. The proximal part of 
the cavity is hemispherical, and the parasite lies with the abdomen 
directed towards the distal end of the spine. The wall of the cavity 
is smooth. Each cavity contained only one Crustacean: a female 
Copepod with two ovisacs. The cavity has evidently been formed by 
the animal; while it was young it has lived near the end of the 
spine in the narrow portion of the cavity; gradually it has grown 
larger and advanced forwards, producing a new and wider portion 
of the cavity. The adult female must remain within the cavity until 
it dies away, but the nauplii slip out through the apical aperture. 
The nourishment of the parasite must be the juices of the spine. 
II. Deseription of the Species, 
Of the two specimens one has been dissected; I wished to 
spare the other. The animal has been difficult to examine, being 
tiny and besides exceedingly swollen and globular (fig. 3), so that 
the area occupied by the appendages is proportionately small, and 
it was impossible to study most of the appendages without a de- 
tailed dissection. Fig. 3 being drawn I cut off the major dorsal 
part of the animal, cleaned the ventral portion of the head from 
the internal side by a small knife as well as possible under one 
hundred degrees of enlargement, examined it and prepared fig. 4, 
finally divided it into small portions and removed gradually most 
of the natatory legs. The result was fortunately so that I have 
been able to produce a tolerably complete description with drawings 
of all appendages (the maxillulæ partly excepted); it may be pos- 
sible that a few setæ on the antennulæ have not been observed and 
that one or two apical setæ on the antennæ and a lateral seta on 
the peduncle of two pairs of natatory legs have been broken off. 
