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 CRUSTACEANS again that myriapods, without being either insects or crustaceans, are possessed of antennae. But the point that chiefly concerns our present subject is the fact that crustaceans are distinguished alike from myriapods and insects by having the pairs of antennae twofold. It cannot be said however that they always make quite as much of this distinction as they might. In the woodlice the first pair of antennae are exceedingly small and often hidden away as if these isopods were ashamed of them. Also in Ta/itrus, the sandhopper, a genus of semi-terrestrial amphipods, a similar diminution occurs. In many of the Entomostraca likewise the first antennae are small and inconspicuous, and that is the case with more than one of the species presently to be mentioned. The Entomostraca are at present divided into three principal sec- tions — Branchiopoda (branchial-footed), Ostracoda (shelly), Copepoda (oar-footed). Not much of the nature in each case can be explained by the mere meaning of the name. The Ostracoda are called shelly because, like some mollusca or shellfish, they have the body capable of a complete enclosure between two valves. But some of the Branchiopoda have a similar bivalvular security, entitling them to boast equally with the Ostracoda that the carapace is their castle. The Copepoda use their feet for locomotion in the water, but so far as that is concerned there are some of the stately phyllopods to which the name of oar-footed would as well or even better apply. The Branchiopoda are divided into Phyllopoda (the leaf-footed), Cladocera (the antlered), Branchiura (the branchial-tailed). The last is by far the smallest of the three divisions, and has in England only a solitary representative, Argulus foliaceus (Linn.). It so happens however that this is among the very few recorded crustaceans of Bedfordshire, yet it comes into the list by what sportsmen would probably call a fluke, for the mention of it is not in any discussion of its own class, but only as incidental to ichthyology. In a paper on ' The Fish of the River Ouse,' Mr. A. R. Thompson observes that ' the Argulus foliace (or roach louse) is also found upon roach and other coarse fish : it is a small crustacean of a disc-shape and attaches itself by means of two suckers on the underside.' 1 It is a vicious little parasite, varying in length when adult from an eighth to nearly a third of an inch. Fishes that would seek revenge by swallowing their foe are soon glad to give it up again. Scientifically it is interesting as belonging to a very small yet distinct and widely-dispersed group. It was at one time placed not in the Branchio- poda but among the parasitic Copepoda. Its mouth organs are con- siderably modified from any normal standard, the first pair of maxillae being evanescent or lost, while the second pair are metamorphosed into suckers. These, as above mentioned, are the organs of adhesion. For sucking the juices of its victim its uses, not the suckers, but its mouth, an efficient apparatus being formed by the sharp glandular organ called the stimulus, and by a combination of the lips and mandibles. 1 Abs. Proc. Tram. Beds Nat. Hist. Soc. and Field Club for the years 1882-3, 1883-4 ( Ma >'> 1885), p. 93. 95