'Lecons sur la Physiol. et l'Anat. comp.' 3 page 197, the statement
that, according to Frey and Leuckart, the heart of Caprella linearis
possesses FIVE pairs of fissures. I have examined perfectly transparent
young Caprellae (probably the young of Caprella attenuata, Dana, with
which they occurred), but can only find the usual three pairs.)

Considering this uniformity presented by the heart in the entire order
of the Amphipoda, it cannot but seem very remarkable, that in the very
next order of the Isopoda, we find it to be one of the most changeable
organs.

In the cheliferous Isopods (Tanais) the heart resembles that of the
Amphipoda in its elongated tubular form, as well as in the number and
position of the fissures, but with this difference, that the two
fissures of each pair do not lie directly opposite each other.

(FIGURE 14. Heart of a young Cassidina.

FIGURE 15. Heart of a young Anilocra.

FIGURE 16. Abdomen of the male of Entoniscus Cancrorum. h. Heart. l.
Liver.)

In all other Isopoda the heart is removed towards the abdomen. In the
wonderfully deformed parasitic Isopods of the Porcellanae (Entoniscus
porcellanae), the spherical heart of the female is confined to a short
space of the elongated first abdominal segment, and seems to possess
only a single pair of fissures. In the male of Entoniscus Cancrorum (n.
sp.), the heart (Figure 16) is situated in the third abdominal segment.
In the Cassidinae, the heart (Figure 14) is likewise short and furnished