SKATES' EGGS AND YOUNG. 625 
foremost part of the embryo; this is made by the protrusion of the optic 
lobes, and closely resembles the same part in the embryos of birds; the 
second (fig. 90, e) is directed downward, and contains the cerebral and 
Fig. 89. olfactory lobes behind which are the eyes. These 
d last, which in the earlier vue as in figs. 86, 88, 
92, are on the same level with the surrounding 
parts, soon become remarkably prominent, as in 
fig. 94, where they rer mind us of the eyes of the 
young of Malleus.* to the fully formed fish they 
> 
orm 
prominent part of the head, in consequence of a 
change of position of the cerebral hemispheres, 
bili rise to the same level with the organs T 
mentioned, as the facial disk (figs. 93, 95, 92, b) 
advances beneath them. In fig. 91 the embryo has 
S; d, proje many of the features of a shark; and in fig. 94, 
e, pee ction of the with the expansion of the pectoral and voiktiat fins,t 
ac nec it begins to take on the form of the skate." 
** Fins. —In the youngest specimen examined (fig. 86), a vertical fold of 
skin stretches along the middle line, from near the head almost to the end 
of the tail above, and from near the umbilical cord to the same point 
elow. "These folds do not pass beyond or become connected around the 
end of the tail. The dorsals (figs. 86 and 93. c) a 
formed by two vertical extensions of the 
fold, and in this early stage of their existence are 

Fig. 90. 
sals. 'The first (fig. 91, d) grows very ra esi 

lobes; e, cerebral lobes 
part by the more rapid growth of that portion of the tail which is in front 
of them, while that om is behind scarcely increases in size, and thus 


* Hammer-headed shark, 
73 
AMER. NATURALIST, VOL. III. 
