no The American Naturalist. [March, 
The eggs were artificially fertilized ; after three hours 
twenty-five minutes, the first cleavage was completed. Twenty 
minutes afterwards four cells had been formed. The time of 
the development of the other phases may be best tabulated : 
Beginning of blastula stage 28 h. " " 
At this stage the free nuclei are very abundant and cover 
about half the yolk. They are much larger and more numer- 
ous just at the edge of the blastula. The blastula stage lasts 
less than half an hour; the embryonic shield is first seen forty- 
one hours after fertiHzation. Two and a half days after fertili- 
zation the optic vesicles appear. The blastopore closes after 
about eighty hours, Kupfer's vesicle and the myotomes appear 
on the fourth day, the heart on the seventh day ; on the twelfth 
the embryos move vigorously ; on the sixteeth day pigment 
spots appear on the top of the head and along the median line 
of the back. The water space which at first was inconsiderable 
has greatly increased. The embroyos were at this time near 
hatching, but, unfortunately died. 
Some larvae of this species procured afterwards show the fol- 
lowing pigment spots: A series along the median line of the 
back from the occiput to the caudal fold ; a spot above the 
posterior portion of each eye ; one medially above the front of 
the eye ; a small one at the nares. A series of spots along the 
median line of the sides ; numerous spots over the air-bladder 
and upon the abdomen. Later a series is formed along the base 
of the anal fold. Yellowish dots are found between the black 
pigment spots of the back and sides. These larvae have a con- 
tinuous fin fold from the abdominal region of the back around 
the tail to the vent ; a smaller fold in front of the vent. The 
embryonic rays are most numerous and best developed at the 
tail. The caudal shows heterocercal tendencies. 
