No. 3-] LATERAL LINE OF AMIA. 525 
quently happens along the lower edge of the lachrymal. Double 
pores of this kind, formed in the adult, usually undergo no fur- 
ther division; but the conditions shown at omg’! in group 11 
operculo-mandibular (Fig. 20, Pl. XX XVI.) can only be explained 
on the supposition that this pore has afterward subdivided and 
multiplied exactly as do the simple pores. 
lieu 1S ang Boley ‘i 
eur pr 
MG eee vi pacers a) 
ee (oO aa, aot: Mal 
: aera oo [OSes 0 
Cut ro. — Diagrammatic representation of the formation of pores and groups of 
pores. The small black spots indicate organs, and the curved outlines openings 
of pits or pores in different stages of formation and division. 
All phases in the formation of half-pores, as well as of the 
primary ones, are shown in Figs. 23 to 34, which fully illustrate 
the development of that part of the infra-orbital canal lying 
immediately behind the eye. The formation of the first few 
pores of the lateral line and the last three pores of the infra- 
orbital are shown in Figs. 35 to 38. 
In Fig. 23, which represents a specimen 19 millimetres long, 
and from twelve to fifteen days old, organ 16 infra-orbital is just 
inclosed, an unpigmented line still marking where the sides of 
the canal have come together above it. Organ 15 lies in a deep 
groove continuous with the canal at organ 16, and is about to 
be inclosed. The inclosing of these two organs is an abbrevia- 
