No. 3.] €HEEK AND SNOUT OF AMIA CALVA. 429 
organs enclosed in sections of canals, and in other fishes related 
to corresponding lines of organs which remain permanently ex- 
posed on the outer surface of the head. Such exposed organs 
are found in Amia in the pit organs of my descriptions (No. 1, 
p. 502), and the parietal of Amia, which lies immediately 
beneath certain of these organs, is apparently a bone developed 
in relation to them; for the parietal of Amia, although it 
encloses a terminal portion of the terminal dendritic system of 
the supraorbital canal, lodges no enclosed sense organ of the 
line. The supra-angular of Amia, which is similarly related to 
one of the dendritic systems of the preoperculomandibular line 
of sense organs, may possibly be similarly related, in its devel- 
opment, either to the vertical cheek line, or to the mandibular 
line of pit organs, notwithstanding the fact that the bone does 
not, in the adult fish, lie directly internal to either of those lines 
of organs. In larvae of Amia the two lines of organs form a 
continuous line extending from organ 8 mandibular to organ 
12 infraorbital (No. 1, p. 534). 
Klaatsch, in the figures illustrating his descriptions, shows 
no terminal buds, canal organs alone, among sense organs, 
being shown as centers from which scleroblastic cells are pro- 
liferated. In his descriptions the terms “ Hautsinnesorgane” 
and “Sinnesknospe”’ do not definitely indicate whether he 
refers to canal organs alone, or to terminal buds also. He, 
however, definitely says (No. 22, p. 220) that what is true for 
the canal bones is true also “zum grossen Theil” for the oper- 
cular bones; and the operculum of Amia, and of all teleosts, 
also, so far as I can find, has no direct relation whatever to any 
part of the lateral-line system. The scleroblastic cells, to which, 
according to Klaatsch, this bone owes its origin, must, therefore, 
either arise from the terminal buds that lie in great numbers 
directly superficial to it, or they must have migrated beneath the 
bone from the canal organs of that canal of the lateral-line sys- 
tem that traverses the wholly separate and independent preoper- 
culum. The latter supposition seems improbable, and Klaatsch’s 
special reference (No. 22, p. 201) to the development of the 
bone seems to definitely exclude it. One is, therefore, led to 
conclude that if Klaatsch’s observations and conclusions are 
