No. 419.] HABITS OF AMEIURUS NEBULOSUS. 915 ` 
water a rich creamy color. The period intervening between 
deposition and the beginning of cleavage is not precisely known. 
After cleavage has begun it continues rhythmically as long as 
it can be followed, the intervals between successive cleavages 
being about thirty minutes. In forty to fifty hours after the 
beginning of cleavage the embryo is plainly visible, measuring 
2 mm. to 2.5 mm. The larvz at the time of hatching are 
about a week old and measure 7 mm. to 8 mm. When they 
break through their surrounding envelopes they are quite 
unable to support the load of food yolk, but lie on their sides, 
now and then making a few vigorous movements. In the 
course of a few days they are able to swim about and soon 
leave the nest accompanied by the male fish. 
During the early summer of 1899 I was able to make some 
further observations on the habits of the larvae. In one of 
the drainage ditches on Cottage Grove Ave., Chicago, they 
were so numerous that in walking a distance of a hundred 
yards one would see from seventy to eighty schools. The 
larva are usually huddled so closely together that they form a 
dark mass, which at a distance appears as a shadow moving to 
and fro. They rarely move in straight paths, but are ever 
circling, apparently in quest of food. When they come in con- 
tact with aquatic plants they pause, carefully search over the 
leaves, and again join in a common movement for other 
grounds. Frequently one departs from the company and darts 
here or there after an insect which may be passing along the 
Surface of the water. One never observes them at rest, as 1S 
common for the adult. During the night they seem " be 
especially active, since it is during this time that they jump 
over the edges of the hatching dishes. E 
The broods vary widely in numbers; One occasionally 
observes a group of forty or fifty and again one oan sms 
Several hundred. It was at first thought that either the num- 
ber of eggs deposited by the different fishes varied accordingly, 
or that a much greater percentage survived in some ice 
While both these factors probably modify the numbers, is 
Chief cause of these wide variations was discovered pct y 
When I chanced to observe four good-sized groups of heo. 
