Dr. R. Kossman on the Entoniscide. 99 
considerably smaller (the trunk at least one fourth, and the 
limbs still more strikingly), we can hardly feel any doubt 
that we have to do with different stages of -age, which are 
passed through within the host. And in this way also it is 
explained why the younger larve, still adapted for this resi- 
dence, which Fraisse and I have met with, possessed so much 
less vitality than those found by Fritz Miiller and Giard ; 
under normal conditions they would only have quitted the 
host after a considerable further development. This is effected, 
as Fraisse and I suppose, by their tearing open the sac in 
which their mother is enclosed, by the aid of the more strongly 
developed last pereiopoda. In numerous attempts to inject 
this sac I have never been able to drive out the fluid through 
any previously existing aperture. Consequently it does not 
seem to me very probable that this sac is one of the internal 
organs of the host; and I therefore incline towards Fritz 
Miuller’s opinion, that it is actually an invulsion of the integu- 
ment, in which the aperture of invulsion may have closed up. 
That the Entoniscide undertake a change of hosts, as 
Fraisse believes, seems to me not very probable. In the first 
place, such a change appears to be unnecessary to bring the 
animal to its definitive locality ; even if no invulsion occurred, 
the same organs which aid the larva in escaping from the 
closed sac would be able to assist it again into a new host. 
Secondly, however, the larva figured by Fritz Miller (2, 
pl. u. fig. 3), as regards the stage of its development, com- 
pletely reminds us of the Bopyrid larva figured by me 
(“Studien tber Bopyriden, II.,” pl. 34. figs. 9,10) as it 
actually attaches itself to the definitive host. This has still 
only a small secondary branch developed on the pleopoda and 
the seventh pereipoda, which must probably have taken place, 
not on an intermediate host, but during free existence. 
EXPLANATION OF PLATE IX. 
Fig. 1. Entione Moniexi, Giard, mature female, seen from the side. 
tions through the cesophagus. 
Fig. 2. The same species, immature female, from the side. 
Fig. 3. Head of the latter in front. 
Fig. 4. Entione Cavolinii, male, from the side. 
Fig. 5, Head of the same, seen from the ventral side. 
Fig. 6. Larva immediately after exclusion. 
Fig. 7. Region of the mouth of £. Cavolinu. a, b,c, d, successive sec- 
8 
. 8. Epithelium of the liver. 
Fig. 9. Ovarian sac. 
Fig. 10. Somewhat oblique section across the oviduct. 
Fig. 11. Section through an immature female. a, liver; 6, fatty body; 
-¢, nervous system ; d, vessel; e, ovary. 
7% 
