L10 CRUSTACEA——-SYNCARIDA CHAP. 
characters are the entire absence of a carapace, and the freedom 
of the eight thoracic segments, with eight free thoracic gangha in 
the nerve-cord; the peculiar double series of plate-like gills; the 
structure of the alimentary canal; and the fact that the eggs, instead 
of being carried in a brood-pouch, or affixed to the abdominal 
limbs, are deposited under stones and among water-plants.’ 
er: 
al 
Pc a 
Pl 
Se 
ee 
2 
y \ |; . 
Fic. 77.—Anaspides tasmaniae in natural position for walking, x 1. ‘The last two 
pereiopods point backwards and are overlapped by the first two pleopods. 
The Peracaridan features, uniting it especially with the 
Mysidacea, are the structure of the elongated heart, the filiform 
spermatozoa, and the fact that no complicated metamorphosis 1s 
passed through, the young hatching out in a condition similar 
to, though possibly not identical with, the adult form. 
The Eucaridan, especially Decapodan, features are the 
presence of an auditory sac on the basal joint of the antennules, 
1 This characteristic is found in the Crustacea elsewhere only in the Argulidae 
and certain Euphausiidae. 
