EMBRYOIvOGY AND LARVAL DEVELOPMENT OF TELEOSTEAN FISHES. I05 



transverse band approximately halfway from the vent to the posterior end of the body 

 extending from the base of the ventral-fin fold onto the dorsal-fin fold. Both black and 

 yellow chromatophores remain associated with the oil globule. 



As development advances the transverse yellow band soon disappears. Before 

 the close of the third day after hatching, when the larval fish are 2.8 to 3 mm. in length 

 (fig- 33). the yellow pigment is greatly reduced. A small yellow area remains just 

 back of the eye, another at the posterior margin of the opercle, and a third over the 

 vent. A little yellow pigment also remains more or less diffusely scattered over the 

 anterior region of the body. The distribution of black pigment also has undergone a 

 marked change. A few small areas occur on the dorsal aspect of the head and the 

 lateral aspect of the anterior region of the trunk. The young fish is marked further by a 

 black spot at the anterior aspect of the vent and a series of black spots near the base 

 of the ventral fin-fold posterior to the vent. At this stage the yolk is completely absorbed 

 and the head is relatively large. 



During the fourth and fifth days after hatching, the larval fish kept in dishes of sea 

 water died rapidly. Few survived until the sixth day. 



In young fish 5 mm. in length (fig. 34) little yellow pigment remains. The black 

 spot at the vent also has disappeared, but the characteristic series of black spots near 

 the base of the ventral-fin fold has become more prominent. The young fish is relatively 

 plump anteriorly and tapers gradually toward the posterior end. 



Young fish 10 mm. in length (fig. 35) show increased pigmentation in the dorsal 

 region of the abdominal cavity. The series of black spots on the ventrolateral aspect 

 of the body still remains. In addition a series of black spots has become apparent 

 along the lateral line over the posterior half of the body. Dorsal, anal, and caudal 

 fins are becoming well differentiated. 



Young fish 25 mm. in length (fig. 36) already show some of the diagnostic characters 

 of the species. The body is relatively plump, but the back is not arched as in the 

 adult, consequently the depth of the body is relatively small. The ground color of the 

 body is brownish yellow. Black chromatophores have increased materially in numbers 

 and are arranged in somewhat irregular transverse bands that give the young fish the 

 transversely banded appearance characteristic of the young of this species. 



PRIONOTUS CAROUNUS (Linn^us). SEA ROBIN. 



Spawning. — This species spawns in June, July, and early August. Fish ripe for 

 stripping were taken in small numbers during the first half of July. Eggs were abundant 

 in the plankton throughout July and were taken in small numbers as late as August 24. 

 The spawn is abundant, and no difficulty was experienced in obtaining and artificially 

 fertilizing eggs for embryological study. 



Eggs. — ^The eggs (fig. 38) are spherical in form and i to 1.15 mm. in diameter. 

 They are slightly yellowish in color, but highly transparent. The yolk sphere contains 

 a variable number (10 to 25) of oil globules of unequal size scattered over the surface. 

 As development advances, some of these oil globules may become aggregated. Usually, 

 however, they remain distributed more or less uniformly over the surface of the yolk. 

 The egg membrane is thin and horny. 



Embryology. — These eggs develop in a manner typical of pelagic teleostean eggs. 

 They are somewhat larger than the eggs of Tautoga onitis, and therefore development 



