J'LEURONECTES AMEKH.W N ITS. 35 



two more or less regular lateral lines on the dorsal surface of the embryo 

 (Figs. 1 and 2). The dots do not extend to the anterior half of the head, 

 nor to the tip of the tail. No pigment is found on the yolk-sac in an\ of 

 the stages here described. Kupffer's vesicle vanishes soon after the closing 

 of the blastopore, as in most of the other species we have examined. With 

 the growth of the embryo the pigment-dots increase somewhat in number 

 and size, without becoming very numerous, reaching their maximum devel- 

 opment about the time of hatching (Figs. 4 and 5). The embryo has a flat 

 spoon-shaped head and a comparatively long body, the tail reaching the 

 head, and sometimes overlapping it, just before hatching. These char- 

 acters serve to distinguish the embryo from that of Ctenolabrus. 



At the time of hatching, the pigment is similar in form to that of the 

 young fish of twelve hours (Fig. 5). The majority of the chromatophores 

 are still rounded dots (.006 to .010 mm. in diameter); those on the head 

 and fore part of the trunk exhibiting thread-like elongations. The yolk- 

 sac has an oblong elliptical form ; this is another feature distinguishing this 

 species from Ctenolabrus. The following measurements were taken from 

 a newly hatched specimen : — 



Total length . 2.85 mm. 



Yolk-sac 85 X -35 " 



Yolk-sac tn vent .......... .4.") " 



Vent to tip 1.45 " 



Width at head .30 " 



Width at otic capsules 20 " 



Twenty-four hours after hatching, the black dots have nearly all van- 

 ished, leaving four black patches, which characterize the remaining stages. 

 One of these patches is seen just above and a little behind the middle of the 

 yolk-sac, a second near the vent, a third half-way from the vent to the 

 tip of the tail, and a fourth near the end of the muscular axis. These 

 spots are all located on the ventral side of the body, and only rarely 

 extend dorsally, as in the case of the third spot in the specimen represented 

 by Fig. 8. 



Dimensions at twenty-four hours : — 



Length 3.00 mm. 



Yolk-sac 75 " 



Yolk sac to vent .50 " 



Vent to tip 1.55 " 



Width of head 35 " 



