DELSMAN: Fish Eggs and Larvae. 101 
which we have seen appear first in the egg on the surface of the yolk. The 
anus is situated under the 50th myotome. Behind this I could count about 
32 myotomes in the tail. Beneath the gut the rest of the yolk is still 
present, in a very elongated shape. The snout has not yet the flute-shape 
of the adult fish. The eye shows the very first trace of a fine pigmentation. 
The pectoral fin is growing out between the second and the third myotome. 
The heart, as mentioned above, was already beating long before the 
hatching of the egg. 
At the upper and the lower border of the myotomes the rudiment 
of two. lateral rows of spines are visible in the shape of two rows of 
little knobs. They may be distinguished even before the hatching of the 
egg. They are best developed near the fore-end of the embryo and in 
the direction of the tail they become gradually less and less distinct. 
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SEG EK KK 
Fig. 4. Larva, two days old, 26x, a, anus, fh, heart, of, otocyst. 
a 
In the morning of the next day, when the larva is one day old, the 
eyes have grown black. Fig. 4 shows a larva 2 days old and 6,5 mm 
long. The underjaw is growing out and now reaches in front of the 
upper-jaw, while in the stage of fig. 3 it is 
shorter than the latter. The two lateral rows of 
backward directed spines have become more 
distinct, especially in the anterior half of the 
larva. The yolk has nearly disappeared. 
I did not rear the larvae longer than two 
days but in the catches made during my cruises 
I found stages which continue the series. Thus | 
fig. 5 represents the head of a larva of a little na 
above 7 mm length. The snout begins to grow h, heart, of, otocyst. 
out into the flute-like shape of the adult. 
This has proceeded much farther in the larva of fig, 6, which has a 
length of 113/, mm. It is not so much the jaws themselves that grow out 
but the part of the skull supporting them. Thus the mouth comes to lie 
at the end of a kind of tube. 
