326 WHITMAN AND EYCLESHYMER. (VoL. 2xie 
had already begun in many of the eggs, while in others it had 
not yet appeared. 
At the end of 10-15 hrs., 100-150 cells have been formed 
in the upper hemisphere, while in the lower, 15—20 grooves are 
present, of which 8-12 have reached the pole. 
To distinguish a stage which marks the beginning of gastru- 
lation is somewhat difficult; if the stage shown in Cut 12 
might be considered as such, the time would be 35-40 hrs. 
after deposition. The process covers a period of 30-40 hrs. 
In 70-80 hrs. after deposition the embryo appears. On the 
7th or 8th day its first movements are visible; these occur 
at long intervals, and last only afew moments. The periods 
of activity become more frequent and vigorous until the 8th 
or oth day, when the envelope is ruptured and the larva escapes. 
The larva at this time measures 5-6 mm. Its body is pale 
flesh color (without pigment), while the large yolk sac is deep 
sepia. The larvae, as soon as they are hatched, attach them- 
selves, by means of their adhesive discs, to the first object met, 
and adhere so firmly that it requires some effort to shake them 
loose. It is impossible at this time for the larva to move its 
load of food yolk. Once losing its hold, it falls heavily to the 
next object, where it again attaches itself. 
At the time of hatching one frequently sees the male fish care- 
fully guarding his nest, in which there apparently is not a single 
living egg or larva, the only evidence of their former presence 
being the fungus-covered débris scattered here and there. A 
careful search, however, among the rootlets will enable one to 
discover the newly hatched larvae. 
During the roth or 11th day the larva reaches a length of 
6-8 mm.; pigment begins to appear in the retina and other 
parts of the head. The pectoral fins have shifted from the 
horizontal to an oblique position; the movements are less vig- 
orous but more frequent. 
In 12-15 days a length of 9-11 mm. is reached. They are 
now deeply pigmented with dark brown. The pectoral fins 
have taken a vertical position. The yolk sac has changed from 
the spherical to an ovoid form, with its smaller end posterior, 
