The Penella crassicornis lives on a hyperoodon; the Penella balænoptera on a Balænoptera musculus among the Loffoden Isles; the Lerneoniscus nodicornis on a dolphin; the great shark of the coasts of Ireland (Scimnus glacialis) generally has a lernean on its eye. My son brought from Rio de Janeiro some Scomberidæ, whose skin is covered with penellæ; and the charming fishes so abundant on the Belgian coasts, which are called Sprot by the fishermen of the country, often have round their eyes strings which might be taken for marine plants, and which are in reality only penellæ. We have found sometimes many individuals on the same fish, stretching
from the head to the caudal region by means of their oviferous tubes, which in certain seasons acquire a pale green tint.
The true Lerneans, such as the Lernea branchialis, a species that was the earliest known upon the different Gadidæ, and which we have observed on the Callionyme lyra, greatly resemble the Penellæ, but their body and their head are much twisted, and with the coils of tubes which contain the eggs, you might take them for a ball of thread. ([Fig. 31.])
Fig. 31.—Lernea branchialis, attached to the gills of Morrhua luscus.
The Sphyriones called Leistera have also a most singular form, and a new species has been recently observed on a fish from the Straits of Magellan. The Conchoderma gracile lives on the branchiæ of the Maïa squinado, the sea-spider of the Adriatic, and Mons. W. Salensky of Charkow, found a copepod crustacean, the Sphæronella Leuckarti, in the egg-pouch of an Amphitoë. The latter parasite has very peculiar characters of conformation and embryonic evolution.
Among the molluscs, the Tunicates give lodging to the greater number of lerneans; in the cavity which is before the mouth, and by which the food passes, some are found which can scarcely be recognized, and which remain there to smell out a feast. The Aplidium of the coasts of Belgium gives lodging to some which are very curious, and which we have named Enterocola fulgens, on account of their colours. The Notopterophorus establishes itself on the body of the Phallusia mamillaris, and a certain number of these parasites are found on the annelids. Professor Sars of Christiania, and Claparède
have carefully described them; and the latter saw on the Spirographis Spallanzani of the bay of Naples, a female which he called Sabelliphilus Sarsii. The genera Selius, Silenium, Terebellicola, Chonephilus, Sabellacheres, Nereicola, &c. infest all the annelids; the Eurysilenium truncatum lives on the Polinoë impar, the Melinnacheres ergasiloïdes on the Melinna cristata.
The echinodermata and the polyps are not free from lerneans; thus the Asterochœres Lilljeborgii fixes itself on the Echinaster sanguinolentus, and we have found a very beautiful species in Brittany on an Ophiurus; the Loemippa rubra, allied to the Chondracanthi, lives upon the Pennatula rubra, the Laura Girardiæ, according to Mons. Lacaze Duthiers, feeds on an Antipathes. A Lœmippus (Proteus) lodges in the cavity of the body of the Lobularia digitata of Delle Chiaie; and lastly, the Enalcyonium rubicundum is sheltered by the Alcyonium digitatum.