Io8 BULLETIN OF THE BUREAU OF FISHERIES. 



advances somewhat less rapidly. The volume of protoplasm in proportion to the volume 

 of yolk is relatively small, yet the blastodisc is relatively thick; consequently, during 

 the early stages of cleavage (fig. 39) the blastoderm covers a relatively small area of the 

 surface of the yolk sphere. 



The first act of cleavage occurs within 1.5 hours after fertilization. The successive 

 acts of cleavage follow each other very regularly. The early blastoderms are usually 

 more nearly symmetrical than are those of Tautoga onitis or either of the other species 

 described. A blastoderm of i6 cells in which symmetry is somewhat disturbed is 

 illustrated in figure 40. 



Within 20 hours after fertilization (fig. 42) the embryo is well differentiated and 

 extends halfway around the circumference of the yolk sphere. The blastopore is not 

 yet closed. The embryo shows 10 to 12 somites and pigmentation has already begun. 

 Numerous yellow and black pigment cells are present over the entire surface of the 

 embryo and in the adjacent areas of the extra-embryonic blastoderm. Pigment cells 

 arise earliest in the embryo and gradually become apparent in the remoter parts of the 

 blastoderm. Yellow pigment arises somewhat earlier than black pigment in these 

 embryos. 



At 42 hours after fertilization (fig. 43) both black and yellow chromatophores are 

 larger and fewer in number than during the earlier stages. They are now sparsely dis- 

 tributed over the surface of the embryo and throughout the extra-embryonic blastoderm. 



Larval development. — Incubation in water at a temperature about 22° C. occupied 

 approximately 60 hours. The newly hatched larvae (fig. 44) are approximately 2.8 mm. 

 in length. The yolk sac is relatively small and still contains oil globules. The head is 

 not markedly deflected. The vent is located just posterior to the yolk sac. The pectoral 

 fins are prominent. The depth of either dorsal or ventral fin fold is greater than the 

 depth of the body posterior to the vent. Black and yellow chromatophores are sparsely 

 scattered over the head, the anterior region of the trunk, and the dorsolateral and 

 ventrolateral aspects of the trunk farther posteriorly. The body is marked further by 

 two transverse yellow bands, one just posterior to the pectoral fins, the other approxi- 

 mately halfway from the vent to the posterior end of the body. These bands of pig- 

 ment extend onto the fin folds. The general color of the head and pectoral fins is yellow- 

 ish. In figures 44 and 45 black pigment is indicated by solid color, while yellow pig- 

 ment is indicated by short lines. 



As development advances a material reduction of the yellow pigment becomes 

 apparent. Five days after hatching (fig. 45) the yellow markings characteristic of the 

 newly hatched larvae are no longer apparent. The head and the pectoral fins still show 

 yellow pigment. Some yellow chromatophores also remain at the vent and at the former 

 location of the posterior transverse band. Black chromatophores are sparsely scattered 

 over the body and a few appear also in the dorsal and ventral fin folds. The posterior 

 caudal region remains practically free from pigment. 



Larval fish five days old have grown to a length of 3.1 to 3.4 mm. The head is 

 relatively large. The pectoral fins are large and prominent. The critical period for this 

 species is reached during the fifth or sixth day after hatching; whea kept in dishes of 

 sea water, few survived until the seventh day. 



Young fish 4 mm. in length (fig. 46) are characterized by a very large head and rela- 

 tively great depth of the body in the anterior region of the trunk. The ground color of 



