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XY. On the Development of the Parasitic Isopoda. 
Bij J. F. Bullae, B.A., Trim Coll., Cambridge. 
Communicated by Dr. Michael Fostee, F.R.S., Prelector of Physiology in Trinity 
College, Cambridge. 
Received March 14, — Read April 4, 1878. 
[Plates 45-47.] 
The following paper contains an account of observations on the development of the 
species Cymothoa cestroides and C. parallela of Milne Edwards ; but the forms of 
the young seem to show that several species are really included under these two 
names. In the early stages of development the only observable difference that exists 
between the embryos is one of size, but in the later stages they differ very markedly 
from each other in their external characters. From adult individuals answering the 
description of C. cestroides I have obtained four varieties of embryos : two with long 
antennae and two with short. 
In the two former the first pair of antennae are but slightly longer than the head, 
while the second pair are longer than the body; the eyes are small. In one of the 
varieties thus characterised the abdominal appendages are fringed with long hairs 
(fig. 20), and in the other they are smooth. 
In the two latter both pairs of antennae are short, and of about the same length, and 
the eyes are large. This group also contains one variety with smooth, and one with 
hairy abdominal appendages. From C. parallela I have obtained but a single form of 
embryo (fig. 21), which differs from the embryo of C. cestroides with short antennae 
and smooth abdominal appendages only in being smaller, and not having so many 
pigment spots on the dorsal surface. 
My work has been mainly carried on in the zoological station at Naples, and I 
take this opportunity of thanking Dr. Dohrn and Dr. Eisig for the kind way in 
which they have forwarded my researches. I have prepared the eggs in the way 
described by Bobretzky (Zeit. fur Wiss. Zool., bd. xxiv.) in his paper “On the 
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* C. cestroides ^ 
l 
Embryos with second pair of antennse long, f 1. Abdominal appendages hairy. 
Eyes small 1 2. Abdominal appendages smooth. 
Embryos with second pair of antennae short. 
Eyes large 
f 8. Abdominal appendages hairy. 
I 4. Abdominal appendages smooth . 
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