68 CRUSTACEA——-COPEPODA CHAP. 
possess a true siphon in which the styliform mandibles work. The 
siphon is formed by the upper and lower lips, which are produced 
into a tube with three longitudinal ridges; in the outer grooves 
are the mandibles, while the inner groove forms the sucking siphon 
(see transverse section, Fig. 36). In Ratania, however, there is 
no siphon. The first antennae possess a great number of joints, 
and may be geniculated in the male (Cancerilla). The members 
of this family live as ectoparasites on various 
species of Echinoderms, Sponges, and As- 
cidians, but they frequently change their 
hosts, and it appears that one and the same 
species may indifferently suck the juices of 
fae me Vinge very various animals, and even of Algae. 
ransverse section 
through the distal part Cancerilla tubulata, however, appears to live 
Sy ene only on the Brittle Starfish, Amphiura 
tum (Asterocheridae). squamata. ; 
Md, mandible. (Aft x 
Gighrechiy, (After "Fam. 7. Dichelestiidae.—The males and 
females are similarly parasitic, and the body 
in both is highly deformed, the segmentation being suppressed 
and the thoracic limbs being produced into formless fleshy lobes ; 
they are placed among the Ampharthrandria owing to sexual 
differences in the form of the first antennae. There is a well- 
developed siphon in which the mandibular stylets work, except 
in Lamproglena, parasitic on the gills of Cyprinoid fishes; the 
succeeding mouth-parts are prehensile. 
The majority of the species are parasitic on the gills of various 
fish (Dichelestium on the Sturgeon, Lernanthropus' on Labrax 
lupus, Serranus scriba, ete.), but Steuer * has recently described a 
Dichelestiid (Mytilicola) from the gut of Mytilus galloprovincialis 
off Trieste. This animal and Lernanthropus are unique among 
Crustacea through the possession of a completely closed blood- 
vascular system which contains a red fluid; the older observers 
believed this fluid to contain haemoglobin, but Steuer, as the 
result of careful analysis, denies this. The parasite on the gills 
of the Lobster, Nicothoe astaci, possibly belongs here. 
The inclusion of Nicothoe and the Dichelestiidae among the 
Ampharthrandria rests on a somewhat slender basis; this basis 
is afforded by the fact that none of the parasitic Isokerandria 
have more than seven joints in the first antennae, whereas 
1 Arb. Zool. Inst. Wien, ii. 1879, p. 268. 201d. Ven L905 ps: 
