42 
fore on the classification of the sensory canals, as far as his criticism 
enlightens us, are based on an unpublished fact in Scomber’, on a 
doubtful condition in Chimaera, and on a misinterpretation of Ewarr. 
2) Here Arııs has somewhat failed to grasp my meaning, and the 
passage in question is, as it stands, too condensed. The point was that 
whilst the independence of the primitive cord of cells was a significant 
fact (but one in which Amia is so far peculiar), the later independence 
of the two canals is involved by the fact of there being a pore at 
their junction — whether this pore be formed by the fusion of half 
or primary pores notwithstanding. The latter quotations from my 
Chimaera paper are of course quite correct, but do not apply to the 
exceptional case of Amia. 
3) As I made no claim to have homologised the bones of the Cod 
fishes skull!), it is difficult to see that I can be blamed for not having 
done so. To accuse me, however, of ambiguity in connection with 
the Post-frontal is not just, since the alleged ambiguity is fully ex- 
plained, and was in fact entirely introduced, by the circumstances de- 
tailed in the post-script to my paper — added as it was passing through 
the press. I referred to a bone as the post-frontal or sphenotic purely 
and simply because that bone actually has received those names in 
Gadus and closely allied forms, and I was anxious to give the full 
synonymy. Further on ALLIS arguing on the basis of the position of 
the dermal tubules and sense organs (in my opinion a dangerous line of 
argument) is led to conclude that the post-frontal +- sphenotic of Gadus 
are homologous with the post-orbital of Amia. Whilst I do not pre- 
tend to the special knowledge of the piscine skull that I freely accord 
to my critic, it seems to me that he is here certainly in error. Firstly 
because the bone in Gadus is, contrary to the bone in Amia, at least 
largely an ossification of the auditory capsule (sphenotic), with however 
I believe a superadded dermal lateral line element (post-frontal), and 
its precise homologue in the Salmon is identified as the sphenotic by 
W. K. Parker, whose opinion demands the fullest respect, and secondly 
because the bone lodging the infra-orbital canal in front of the squamosal 
would then be the post-frontal in both our types. Auuis on the other 
hand homologises my post-frontal + sphenotic with his post-orbital, and 
my sub-orbital 6 with his post-frontal. To my mind these comparisons 
are from his own point of view quite inadmissible, since the two bones 
would then occupy exactly reverse positions in the two forms, and if, 
as he claims, the topographical relations of dermal tubules and sense 
organs have any value, I should expect the same relations of the cranial 
bones to have a still greater value. I contend however that these 
homologies can only be maintained on developmental evidence, and not 
on the position of a variable series of characters. 
4) I have already dealt with my alleged ambiguity in the use of 
the terms post-frontal and sphenotic, and pointed out that the charge 
cannot justifiably be preferred against me. With regard to the re- 
mainder of the paragraph, it contains its own answer and I do not 
therefore propose to discuss it. 
5) In the preceding paragraph, be it noted, my critic expresses sur- 
1) This is emphasized in a footnote to my paper. 
