414 



BULLETIN OP THE BUREAU OF FISHERIES. 



embryo than the melanophores. Figure lo is an attempt to illustrate the distribution 

 of chromatophores on the embryo and in the extra-embryonic blastoderm about 48 

 hours after fertilization. No attempt is here made to distinguish between black and 

 yellow chromatophores. The .embryo is now segmented throughout and circulation is 

 established. The chromatophores in the extra-embryonic blastoderm show a marked 

 tendency to become aggregated along the larger blood vessels. 



As development advances the yolk mass becomes materially reduced. At 72 

 hours after fertilization (fig. 1 1 ) the embryo appears relatively large and plump. The 

 posterior portion of the body is free from the yolk and moves freely within the egg 

 membrane. 



As the time of hatching approaches the yolk mass may be reduced to half its original 

 volume. The embryo is well developed and exhibits a characteristic distribution of 



CyPRINODON VARJEG.\'ms. 



Fig. 9. — Egg showing aa early stage in Fig. io. — Egg 48 hours after fertilization. FlG. ] 

 differentiation cf cmbr^'O. 



-Egg 72 hours after fertilization. 



chromatophores. It remains relatively short and plump. Its length usually does not 

 exceed the circumference of the egg. 



Larval development. — Incubation at laboratory temperature occupies five to six 

 days. The newly hatched larvae (fig. 12) are approximately 4 mm. in length and rela- 

 tively plump. The yolk sac remains relatively large but the head is not deflected. The 

 dorsal fin fold has its origin relatively far posteriorly. Both dorsal and ventral fin 

 folds are continuous. The depth of each fold is less than half the depth of the body 

 posterior to the vent. The vent is located at the posterior margin of the yolk sac. The 

 larva is slightly yellowish in color and the posterior half of the body is marked by lighter 

 and darker vertical bands. 



At five days after hatching (fig. 13) the yolk is almost completely absorbed. The 

 larvae are now 5 mm. or over in length. The head has become bluntly pointed and the 

 depth of the body has somewhat increased. The general color remains slightly yellowish 

 and the vertical bands are somewhat more conspicuous than in the preceding stage. 



Figure 14 illustrates a young fish 9 mm. in length. At this stage many of the 

 characters of the adult are already apparent. The body is relatively slender, however, 

 and the back is not yet elevated. The vertical bands characteristic of the species are 

 present but not fully developed. 



