24.2 BOPYRIDA. 
In addition to Mr. Templeton’s specimens, we have 
received the male and female of this species from Pol- 
perro, collected by Mr. Couch, as well as a coloured 
drawing of a specimen which we also consider to belong 
to this species from St. Andrews ; having been taken by 
Mr. McIntosh. It was first found by Rathke upon 
Pagurus Bernhardus on the Norwegian shore. 
Athelque fullode of M. Hesse, Ann. Sc. Nat., ser. 4, 
vol. xv. p. 97, pl. 9, appears to us to belong to this 
species. 
With reference to the question how the Bopyrus can 
survive when the crab throws off its exuvium, Dr. Fritz 
Miiller writes to us—“‘ When the crab casts its skin, 
there can be no doubt but that the Bopyrus must go 
along with it; but as the crab, immediately after exuvia- 
tion, is in an almost helpless and motionless condition, I 
think that the Bopyrus may crawl again into the branchial 
cavity. I shall send you a Porcellana, the integuments 
of which are so soft that it must have moulted very 
recently, and notwithstanding it has a very large Bopyrus 
in its branchial cavity. Moreover, it seems to be im- 
possible that the considerable deformation of the carapace 
of the crab produced by the Bopyrus could disappear by 
exuviation ; but I never found a deformed carapace with- 
out the Bopyrus, although I have examined more than a 
hundred Porcellanz bearing the parasite.”—‘ I may here 
observe, in Bopyrus Porcellane the right side is more 
developed than the left when the parasite dwells in the 
right branchial cavity, whereas the left side is the larger 
when the Bopyrus dwells in the left branchial cavity. 
The Bopyrus being fixed with its head directed backwards 
naturally in the right branchial cavity, the right side of 
the parasite can freely extend downwards, and therefore 
becomes larger.” 
