132 



BULLETIN OF THE BUREAU OF FISHERIES. 



on the surface of the yolk sac adjacent to the body, and on the ventrolateral aspect of 

 the body near the base of the ventral-fin fold. 



Three days after hatching (fig. 120) the young fish have grown to a length of 6.2 to 

 6.5 mm. The general color of the body remains yellowish, and the distribution of black 

 pigment remains essentially as in the newly hatched larvae. However, the chromato- 

 phores have increased materially in number. 



Eight days after hatching (fig. 121) the young fish have attained a length of ap- 

 proximately 7 mm. The general color of the body is now darker than in the earlier 

 stages. Black pigment has become more abundant, and the yellow pigment is ma- 

 terially reduced. Black chromatophores are present over the entire surface of the body 

 but are closely aggregated only on the dorsal and dorsolateral aspects. 





Fig. 119. — Newly hatched fish, actual length 4,3 mm. 



Fig, 120. — Larval fish 3 days after hatching, actual length 6.3 mm. 



\ i ,1, ■ / '"-^^ 



•^"n- -- »-*----~"*-^-i--*' -■ 



^S^^S?- y 



Fig. 121. — Larval fish 8 days after hatching, actual length 7 mm. 

 GASTEROSTEUS ACULEATUS. 



APELTES QUADRACUS (Mitchill). FOUR-SPINED STICKLEBACK. 



Spawning. — This species is known to spawn in May and June (Sumner). The 

 spawning season continues until late in July. Females ripe for stripping were taken as 

 late as July 24. A considerable number of females were taken on August 3 but all were 

 spent. As in the case of Gasterosteus aculeatus, males ripe for stripping were not secured. 

 Fertilization was accomplished by macerating the testes of the male in the water into 

 which the eggs were stripped. 



Eggs. — The eggs are demersal and adhere firmly in small clumps. They are 

 similar to the eggs of G. aculeatus here described but more intensely yellowish and 

 consequently more opaque. They are somev^hat irregular in form when stripped from 



