86 Dr. R. Kossman on the Entoniscide. 
freely, and supposed that the ova were introduced into a sub- 
sequently-produced lumen of these leaves, which, for an 
Isopod, or, indeed, for any Crustacean, would be truly as- 
tounding. 
Tf one kills the Hntoniscus very quickly, the sac in which 
it lies can be easily removed after some time; if the Hnto- 
niscus be kept living for some days in sea-water, this sac, not 
being a part of the parasite, begins to macerate and separate” 
in rags. In this way we easily ascertain that the animal has 
two pairs of greatly-developed brood-leaves, both of which 
are inserted on the ventral surface close behind the head, and 
of which the anterior pair is bent far forward and upwards 
beneath the head, whilst the hinder pair extends backwards 
as far as the pleon. ‘These brood-leaves are constituted 
exactly like those of the Bopyride &c.; 7. e. they are thinly 
membranous, with a venation of chitinous thickenings. The 
anterior margin of the anterior leaf, which, by curvature, 
becomes dorsal (in the figure the nght leaf is omitted for the 
sake of clearness), curls a little inwards. ‘These anterior 
brood-leaves receive the eggs more especially between them- 
selves; the posterior ones, which show a faint venation, 
receive the ova rather between them and the wall of the body. 
Of course the wall of the sac in which the parasite lies assists 
in completing the closure of the brood-chamber, just as in 
Bopyrus &c. the same thing is done by the gill-cover of the 
host; but there is absolutely no trace of any amalgamation 
or other union of the right and left brood-leaves, and the 
brood-chamber of the parasite is therefore not in itself closed. 
The differences between the females of the two genera Ento- 
niscus and Entione are not inconsiderable. I shall dwell 
here also first of all upon the external characters. 
The chief distinction relates to the pleon. This in Ento- 
niscus is distinctly segmented, six-jomted; the first five 
segments bear each a pair of inarticulate sabre-shaped un- 
setigerous feet, which are in fact considerably longer than 
the segments to which they belong. In Hntione, on the 
contrary, the pleon is unsegmented, and, instead of sabre- 
shaped, it bears leaf-shaped appendages, of which the anterior 
are the largest and have a strongly frilled margin; the last 
pair, marked Lin Fraisse’s figure (4, pl. u. fig. 7), is quite 
smooth. 
While in Lntoniscus the pereion is furnished with six pairs 
of large much laciniated brood-leaves, the posterior ones in 
Entione, especially in the fully developed stage, are rudimen- 
tary. In younger females, as Fraisse and Giard repeatedly 
indicate, traces of them may be found. On the other hand, 
