318 
BULLETIN OF THE BUREAU OF FISHERIES 
13 .75-millimeter stage . — Total length, 13.75; length to vent, 13.0; greatest depth, 
1.6; diameter of eye, 1.1; myomeres, 33 to vent plus 10+ behind. Head character- 
ized by terminal, "horseshoe-shaped” mouth, and very large eye. Dorsal marginal 
fin fold very narrow, the later position of true dorsal indicated by a slight rise ; ventral 
marginal very wide, extending forward almost to base of pectoral; caudal lophocercal 
with few rays apparent; no ventrals. 
Pigmentation. — Body is colorless except for silver eyes edged in black, and black 
chromatophores distributed in four definite bands: (1) Group of stellate chromato- 
Figure 19. — Catostomus commersonii, 13.75 millimeters 
phores on top of head followed by a triple line along dorsal ridge to end of body; 
(2) series of linear chromatophores along mid-lateral line of myomeres, about 56 
from behind head to end of tail; (3) series starting behind head, congregated over 
dorsal surface of air bladder and continuing in massed line (about 4 chromatophores 
wide) to vent, mostly subsurface; and (4) series of about 57-60 large round and stellate 
pigment spots along ventral ridge from behind head to vent, thence as a massed line 
of about 4 chromatophores wide to end of body. Caudal fin fold is peppered with 
very small chromatophores near its base. 
14.3-millimeter stage . — Total length, 14.2 standard length, 12.9; length to vent, 
10.1; length of head, 2.75; greatest depth, 2.2; diameter of eye, 1.0 millimeters. 
Myomeres, 33 to vent plus 10 + behind. Snout less blunt; air bladder two-chambered. 
Dorsal fin developed with evidences of 10 rays, and suggestion of about 4 anal rays; 
ventrals developing; caudal heterocercal; embryonic marginal fin fold persisting 
behind dorsal and complete on ventral aspect. 
Pigmentation. — The pigmentation here is essentially as in the previous stage, 
with the addition of more chromatophores in the caudal, and a few stellate ones in 
dorsal fin. The extreme transparency of a living specimen reveals many subsurface 
chromatophores: One series above and another below the nerve chord, connected 
laterally at intervals corresponding to the myomere interspaces, and a third series 
marking the ventral aspect of the notochord. Gill arches are likewise margined with 
subsurface chromatophores. 
20 .5 -millimeter stage . — Dorsal and anal fins complete. 
