EMBRYOLOGY AND LARVAL DEVELOPMENT OF TELEOSTEAN FISHES. 1 27 



MENIDIA MENIDIA NOTATA (Mi(chill). SILVERSIDE. 



Spawning. — This species spawns in June and July. The height of the spawning 

 season is reached, doubtless, before July i. The great majority of the fish taken early 

 in July were already spent. 



Eggs. — The eggs are spherical in form, i.i to 1.2 mm. in diameter. They are 

 demersal and are held together in ropy clumps by a tangle of adhesive threadlike 

 processes, a tuft of which arises from the membrane of each egg. The yolk sphere 

 contains 5 to 12 large oil globules of unequal size and numerous smaller ones. The 

 larger oil globules may or may not be aggregated ; the smaller ones are distributed more 

 or less uniformly over the surface of the yolk. The eggs are yellowish in color and semi- 

 transparent. The egg membrane is thick and the micropyle relatively large (fig. loi). 

 These eggs are very similar to those of the related species, Kirtlandia vagrans, described 

 in an earlier paper," but are somewhat larger. 



Embryology. — These eggs, being somewhat larger and much more heavily laden 

 with yolk material, develop much less rapidly than do the pelagic eggs here described. 

 In all other essential respects their embryological development follows a course prac- 

 tically identical with that as outlined for the eggs of Tautoga onitis. Successive stages 

 in the process of cleavage and the differentiation of the embyro are illustrated in figures 

 102 to 106. The embryo is well differentiated and shows 20 to 24 somites within 40 

 hours after fertilization (fig. 106). 



The beginning of pigmentation is observed during the third day of incubation. 

 Black chromatophores become sparsely scattered over the embryo and the extra- 

 embryonic blastoderm. Yellow chromatophores appear only on the embryo. As 

 development advances, black chromatophores become aggregated in a few areas on the 

 dorsal aspect of the head and in a series at the base of the ventral-fin fold. A few black 

 chromatophores appear at the base of the dorsal-fin fold near the posterior end of the 

 body. The black chromatophores in the extra-embryonic blastoderm gradually become 

 arranged along the extra-embryonic blood vessels. Small yellow chromatophores 

 remain sparsely scattered over the embryo for some time, but gradually become less 

 conspicuous. 



Larval development. — Incubation at laboratory temperature occupied 8 to 9 days. 

 The newly hatched larvae (fig. 109) are approximately 5 mm. in length and relatively 

 slender. The yolk is largely absorbed before hatching. The vent is located just pos- 

 terior to the yolk sac. From this level the body tapers gradually toward the posterior 

 end. Black and yellow chromatophores are aggregated on the dorsal aspect of the head 

 and in the dorsal region of the abdominal cavity. Black chromatophores are present on 

 the ventral aspect of the yolk sac, in a series at the base of the ventral-fin fold, and in 

 a few small groups at the base of the dorsal-fin fold toward the posterior end of the body. 



Five days after hatching (fig. no) the larvae have grown considerably, but the 

 majority of them do not exceed 5.5 mm. in length. The yellow pigment is materially 

 reduced. Black chromatophores have become more abundant on the dorsal aspect of 

 the head and anterior trunk region. The body is marked further by a series of black 

 chromatophores at the base of the ventral-fin fold and another at the ventral level of 

 the notochord. 



Kuntz, A.: Notes on the embryology and larval development of five species of teleostean fishes. Bulletin. Bureau of 

 Fisheries, vol. xxxiv, 1914, p. 420. 



