306 Transactions.—Zoology. 
On re-reading the paper of Professor Huxley's referred to in the fore- 
going quotation,* it appears to me that Mr. Chilton has been misled by 
having taken a useful and suggestive table of morphological characters for a 
natural classification. A very similar table is given in Huxley’s paper on — 
Ceratodus,t in which the Ichthyopsida are divided, according to the mode of 
attachment of the mandible, into Autostylica; Amphistylica, and Hyostylica, 
but it is certainly not intended to convey the impression that the Dipnoi 
are more nearly related to the Amphibia than to the Ganoids from the fact 
that the two former belong to the Autostylica, while Ganoids are hyostylic. 
It is evident from even a casual examination, and is implied, although 
not stated explicitly, in the paragraph of Huxley’s paper beginning :—* Let 
it be supposed,” t that the Potamobiide and the Parastacide are more nearly 
allied to one atio than is either of them to any other family of Crustacea. 
To say that the Parastacide are more nearly allied to the Palinuride than 
to the Potamobiide, because they are astylic, is not more reasonable than 
to say that Anguis is more nearly allied to the Ophidia than to the Lacertide, 
because itis apodal. In the same way, to unite the Parastacide with Pa- 
linurus, and to separate them from the Potamobiide, on the ground that the 
two former possess a more primitive type of male reproductive apparatus 
than the latter, is equivalent to grouping Ganoids with Elasmobranchs. 
rather than with Teleosts, because of the abnormal condition of the urino- 
genital organs in bony fishes. 
What Professor Huxley shows clearly enough is that, while the Homarina 
are more closely allied to the Potamobiide than to the Parastacide, the 
reverse is the case with the Palinuride. He does not discuss the question 
of the origin of the latter family, nor say whether he considers its affinities 
to be, on the whole, Astacine or Homarine.| It is perhaps an open ques- 
tion whether true genetic affinities are more clearly indieated by the loss of 
the first abdominal appendage, and by the structure of the male organs and 
the sete, or by the structure of the gills; but, at any rate, it must not be 
forgotten that Palinurus agrees with the Homarina in having the podo- 
branchs completely divided into gill proper and epipodite and thus differs 
widely, in an important structural peculiarity, from the Parastacide. 
However, this may be, it is certain that the interval separating Pali- 
nurus from the Parastacide is far wider not only than that which separates 
the latter from the Potamobiide, but than that existing between the Astacina 
and the Homarina. To hold otherwise is equivalent to denying the value 
of both anatomy and embryology as guides to genetic affinity. 
*On the Classification and the Distribution of the Crayfishes, Proc. Zool. Soc., 
1878, p. 752. 
t Proc. Zool. Soc., 1876, p. 2 1 Quoted by Chilton, loc. cit., p. 152. 
|| Boas, in the paper referred x above, seems to derive Palinurellus from a Homarine 
ancestor. 
