320 ROY L. MOODIE 
Sagemahl’s (’91) objection to the value of this system as a 
criterion of homology in the skull of the Cyprinidae has been 
satisfactorily explained by Allis (04), who, on an examination 
of three genera of this family, learned that ‘‘it is the parietal 
bones of these fishes, and not their supratemporal canals, that 
are not the homologues of those in the other fishes.’’ Allis in 
the same paper goes on to discuss and figure, in twelve plates, 
the relationship of the latero-sensory canals to definite bones 
of the cranium as established in twenty-one genera in fishes. 
The value of the canals in homologizing the bones of ancient 
Amphibia and fishes the writer has likewise pointed out, and 
there is a firm basis for stating that this system of canals 
is one of the most constant features of primitive vertebrate 
organization. 
The antiquity of such an arrangement as seen in the heads 
of modern fishes is suggested by the condition of the latero- 
sensory canals described by Bryant (’19) in Eusthenopteron 
foordi from the upper Devonian rocks of Scaumenac Bay, Que- 
bec. The nature of the sensory canals of the head among the 
Triassic fishes of Spitzbergen has been discussed in an especially 
fine way by Erik A. Son Stensi6 (21). This plan (fig. 1) out- 
lined so early in vertebrate organogenesis has since suffered 
little change. 
Unfortunately, the skulls of modern Amphibia are seldom cut 
by the latero-sensory canals, but we have the work of Harrison 
(04) to show that the lateral line of amphibians is of taxonomic 
importance, and I have shown (’16) that the lateral-line system 
as preserved on Carboniferous Branchiosauria is essentially like 
that of the modern urodeles, especially Necturus. 
LITERATURE 
Such being the condition of our knowledge of the relationship 
of the bones of the head and the latero-sensory canals, I under- 
took to determine if the cranial bones developed in response to 
the sense organs or to the canals after they were fully supplied 
with the sensory endings. The only literature which has a 
direct bearing on the problem is the study of Klaatsch (’94), 
who has discussed, in connection with many other problems, 
