. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 104 CALIFORNIA FISH AND GAME The eggs of Exocoetus sp. from the "Shellback" expedition collec- tions have a diameter of about 3 mm. The capsule is smooth and transparent, colorless or faintly pink, and completeh^ lacks filaments, spines, or other modifications. Superficiall}^, these eggs are therefore essentially similar to those of most known allotriognaths. In early stages the embryos of Exocoetus and those of allotriognat
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. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 104 CALIFORNIA FISH AND GAME The eggs of Exocoetus sp. from the "Shellback" expedition collec- tions have a diameter of about 3 mm. The capsule is smooth and transparent, colorless or faintly pink, and completeh^ lacks filaments, spines, or other modifications. Superficiall}^, these eggs are therefore essentially similar to those of most known allotriognaths. In early stages the embryos of Exocoetus and those of allotriognaths are much alike, especially in the large yolk sac, the absence of an oil globule, the proportions of the large bulging head and the long narrow body axis, the long gut that extends well back beyond the surface of the yolk sac, and the rather early development of the pectoral fin buds. In these early stages there are, however, already some distinct dif- ferences that forecast the great divergence of these two groups of fishes in their later embryonic development. In the allotriognath embryo the heart is in the t3'pical chordate position, under the neck, and it remains in that position throughout embryonic development; in the synentognath embryo the heart is displaced forward onto the front of the yolk sac. In the allotriognath the tail tip remains in the sim]ile, straight, embryonic condition; in the early synentognath embryo the tip of the notochordal axis enlarges and bends upward, the fin fold widens around it, and the definitive hypural and ray elements become large and well defined long before hatching. Allotriognath fishes, insofar as their early stages are known, are remarkable for the extreme elongation of one or more of the anterior dorsal rays in the advanced embryonic stages and in the larvae. This specialization is presaged in the early embrj^o b}^ the precocious formation of a small knob-like enlargement on the mid-dorsal line in or slightly anterior to the pecto