TEMNODON SALTATOE. 15 



closing of the blastopore, — the chromatophores are usually larger than in the 

 stage of Fig. 6, but less numerous. Up to this time no pigment appears on 

 any part of the yolk except around the oil-globule. The brownish yellow 

 pigment consists of rounded or branching cells scattered along the body from 

 tin- head to a point just behind the vent. The black cells reach farther 

 back, and are all placed at the dorsal angles of the myotomes. In nearly 

 all the black cells of this stage one or two brownish yellow granules (.01 mm.) 

 may be seen. By this time most of the black chromatophores have taken 

 an angular or coarsely branched form. 



The measurements of this stage are as follows : — 



Total length, 2.15 mm. 



Yolk-sac, 75 X -40 " 



Yolk-sac to vent 275 " 



Vent to tip 1.00 " 



Width of head, 275 " 



Height at anterior end of yolk-sac, ...... .575" 



Height at posterior " " 50 " 



Yellow pigment-spots appear along the edge of the dorsal fold in the 

 next stage (Fig. 8); but these become smaller by the fourth clay (Fig. 10), 

 and wholly disappear between the fifth and ninth days. In all the remaining 

 stages of Plate IV., and up to the fifth day, the black pigment undergoes 

 very little change. The yellow pigment reaches its highest development in 

 the course of the first two or three days, and never extends much beyond 

 the anterior half of the fish. From the ninth day onward (Fig. 11 and the 

 following) it takes a diffuse form, and becomes less and less prominent until 

 it finally disappears. In the earlier stages here figured, the dorsal fold is 

 well arched, and its height and proportions scarcely undergo any notable 

 changes during the first nine days. Between the fifth and ninth days the 

 eye assumes the blue color seen in all the subsequent stages. The upper 

 side of the eye alone is black. 



In the stas:e seen in Fi»\ 12 we find a dorsal and ventral row of black 

 chromatophores in the posterior half of the body, which mark the region of 

 thickening for the dorsal and anal. At the bases of the hypaxial rays of the 

 caudal lobes are to be seen four or five spots, which may be regarded as a 

 continuation of the ventral row. There is a concentration of black pigment 

 along the intestinal tract, another in the upper part of the eye, ami a third 

 on the hind part of the head. In the remaining stages the pigment becomes 

 more strongly developed in these different regions, and in the last stage the 



