496 ALELS: [ VOL. Tr: 
Pore 3 of the supra-orbital line and the corresponding one of 
the opposite side form a prominent pair about half way between 
the nasal apertures. Pores 6 infra-orbital and 4 supra-orbital 
lie close together near the posterior nasal aperture, No. 6 in 
front of, and No. 4 median to, it. No. 5 supra-orbital lies imme- 
diately behind No. 4, about on a level with the anterior edge of 
the eye; No. 6 nearer the middle line on the top of the head, 
between the eyes; and No. 8 behind and median to the double 
pore 15-7. 
Pores 1 to 10 of the operculo-mandibular line lie along the 
lower edge of the jaw, No. 1 markedly in front of the curved 
line of the others. No. 11 lies almost directly above No. Io, 
and has in the 674-millimetre specimen undergone its first divis- 
ion, the two secondary pores lying, as in the adult, one on 
either side of the end of the supramaxillary furrow. Pores 12 
to 16 lie along the edge of the pre-operculum, Nos. 13 and 14 
already double in the larger specimen. 
In the supratemporal cross-commissure there are two pores 
on either side, and one in the middle line of the head. 
The central canals at this age are inclosed in thin, bony tubes 
which in certain places, as in the suborbital series (Cut 9), 
represent the entire bone of the adult. In others, as in the 
squamosal and frontal, the tube lies along the edge or toward 
the middle of a thin, bony plate of the same thickness as the 
wall of the tube, and the tube and plate together form the bone. 
In young larve, where the bones are just beginning to develop, 
they are represented by short, semi-cylindrical pieces lying im- 
mediately below each organ. At this stage they correspond to 
the short, bony scales which, according to Bodenstein (No. 3, 
p. 131), partly inclose each organ of the lateral line in the adult 
of Cottus, and to the bony half-rings which, according to Leydig 
(No. 9, p. 251) and Solger (No. 14, p. 111), support the walls and 
protect the organs in the cranial canals of Chimzera monstrosa. 
These semi-cylindrical pieces in Amia increase in length and 
soon become open gutters or channels. The plate then appears 
along the sides or toward the bottom of the channel, always 
continuous with it and growing from it on either side. The 
canal and the gutter in which it lies are always at this stage on 
the upper surface of the bone, thus corresponding to the con- 
ditions described by Bodenstein (No. 3, pp. 132 and 143) in the 
