4.6 A HISTORY OF RECENT CRUSTACEA 
or devoted to other purposes. They may be partially or 
entirely branchial. Among the Stalk-eyed Crustacea they 
are often used in the female for retaining the eggs during 
an early period of development or hatching.. In the 
Amphipoda the fourth and fifth pairs are more or less 
adapted for springing, and bear the name of uropods, or 
tail-feet. This name is also given to the appendages of 
the twentieth segment whenever they are present. ‘These 
are prominent features in the Cumacea and most other 
Edriophthalma, and in the Macrura they combine with the 
telson to form the powerful tail-fan, for which Mr. Spence 
Bate has proposed the Greek name rhipidura (see Plate X.). 
In the Copepoda there is a ‘ caudal furca,’ homologous with 
the caudal rami in the Nebaliidee, which must be distin- 
guished from the terminal uropods of the higher Crustacea, 
as ‘ being not true limbs, but more properly representing a 
bipartite terminal segment.’ ! 
21. The telson is extremely variable in form and 
relative size, and sometimes by coalescence with the pre- 
ceding segment shows little trace of independent exist- 
ence. ‘The intestinal canal opens on its under side. It 
is sometimes deeply cleft, as though the two terga, or 
dorsal plates, of a body-ring had come apart. To prove 
its claim to be regarded as a segment, the most effective 
argument would be to show that it sometimes carries 
appendages after the fashion of all the other segments. 
Bell, in the ‘ British Stalk-eyed Crustacea,’ says that he 
has frequently observed appendages to the telson of the 
common prawn, Leander serratus (Pennant), ‘in the form 
of extremely minute points attached to the very extremity 
of the segment, and moveable.’ Spence Bate says, ‘In 
some genera, or even families, the telson is posteriorly 
rounded, as in the Astacidze; in others it is anteriorly 
hard and calcareous, and posteriorly soft and membranous, 
as in the Synaxidea, a circumstance that is suggestive of 
a distinct relationship of the two parts, the anterior 
which carries the anus belonging to the normal somite, 
' Sars. Ecport on the Phyllocarida collected by H.M.S. Challenger, 
p. 35. 
