152 Transactions:— Zoology. 
The most important result arising from the examination of Paranephrops 
setosus is that its affinity to Palinurus now seems to be placed beyond doubt. 
Paranephrops and the Parastacide generally resemble the Palinuride in 
that they have no appendages upon the first abdominal segment ; in this 
they differ from the crayfishes of the Northern Hemisphere, and from 
Homarus and Nephrops. The Palinuride and the Parastacide also agree in 
having hooked setw,* while in the Potamobiide and in the lobsters the 
sete are not hooked. Moreover the branchial formule of Palinurus and 
and Paranephrops are almost identical. Taking the presence or absence of 
the first abdominal appendages as the basis of his classification, Professor 
Huxley placed the Palinuride and the Parastacide together as the Astyla, 
while the Potamobiide, Homaride, ete., together form the Stylophora. This 
classification is confirmed by the strueture of the male reproductive organs 
in Paranephrops setosus, for these agree in every essential particular with 
those of Palinurus vulgaris as described by Brocchi.t In both the testes 
consist of two long tubes united towards their anterior ends by a commis- 
sure; both have long convoluted vasa deferentia ; and in both the extremi- 
ties are greatly expanded. This would appear to be the oldest and most 
generalized form of the male reproductive organs of crayfishes, New Zea- 
land having preserved the old form in this as in many other cases. In 
Astacus jluviatilis the testes are very different in shape; they are trilobed, 
two lobes being directed anteriorly, and one posteriorly: thus the two pos- 
terior portions, which in Paranephrops and Palinurus are quite distinct, 
appear in Astacus fluviatilis to have coalesced into a single mass. The vasa 
deferentia of Astacus are much convoluted, but their extremities are not 
expanded or at least only slightly so. Professor Huxley gives them without 
any expansion,+ but in Milne-Edwards’ figure they are slightly expanded.$ 
The male reproductive organs of Homarus vulgaris appear to be intermediate 
between those of Paranephrops setosus and of Astacus fluviatilis, for in them 
the two posterior portions are close together and apparently confluent, 
though not so perfectly coalescent as in Astacus; the vasa deferentia are 
curiously enough not convoluted, though their extremities are considerably 
expanded. : 
Ín aecounting for the origin and present distribution of the crayfishes 
Professor Huxley says :—“ Let it be supposed that, at some former period 
* Huxley, “ On the Classification and Distribution of the Crayfishes." Proceedings 
of the Zool. Soc., 1878, pt. iv., p. 776. 
t Annales des Sciences Naturelles, Sé. VI., ii. 
1 ** The Crayfish,” p. 130. 
$ Hist. Nat. des Crust., Atlas, pl. 12, fig. 14; or the artic e “ Crustacea” in Todd's 
Encyclopedia of Anatomy and Physiology. p. 783 
|| Milne-Edwards' Hist. Nat. des Crust. tall pl. 12, fig. 15. 
