SPECIES NO. 25. 47 



The body tapers gradually from a point just behind the otic capsules to 

 the end of the tail. The margin of the ventral fold is slightly notched at the 

 vent. 



The next stage (Fig. 5). twenty-four hours old, shows the chromatophores 

 in a half-contracted state, distributed mainly in the four legions before 

 named. There is a small admixture of black pigment, and the sienna 

 pigment is now advancing over the yolk-sac. 



At the age of seventy-two hours (Fig. 0) the entire yolk-sac is covered 

 with sienna pigment and a few large, branching black cells. The head and 

 trunk arc diffusely colored, with stronger pigment-spots around the eye and 

 front of the head. A coarsely branching spot is seen at the origin of the 

 pectoral, and another above the pectoral. A streak of brownish and blackish 

 spots runs along beneath the chorda from the pectoral to the caudal region 

 of chromatophores. A single black cell is seen at the end of the chorda. 

 The entire surface is now roughened with prominent granular cells, a few 

 of which are sketched on the median folds. 



The stage represented in Fig. 7 (four days) is so totally unlike the 

 preceding stages that it is difficult to believe it is the same species. It is 

 somewhat surprising that in both the species Nos. 23 and :>•"> the yellow 

 pigment-spots should lie followed by so different a coloration (compare Figs. 

 9 and 10 of Plate XVIII. and Figs. G and 7 of Plate XIX.). It will be inter- 

 esting to see to what species these embryos belong. Something very similar 

 in the variation of the chromatophores has been observed in successive stages 

 of Ctenolabrus. The eye is now blue, and most of the pigment of the 

 body has disappeared. The sienna pigment is represented by three or four 

 patches of yellow, and the black by three coarsely branched cells about 

 midway of the body and one large cell near the vent. This embryo has 

 retained rather the embryonic fin-folds of earlier stages (Fig. 5) than those 

 of the stage immediately preceding (Fig. G). 



To facilitate the identification of the different pelagic stages of Fish 

 and Fish eggs, the following table has been prepared. It gives the most 

 characteristic features of the egg and the young of each stage, with special 

 bibliographical reference- 



