11 
In nature, although many of the eggs are eaten by other fish 
and even by the mother, the majority of them sink to the bottom 
in mud and are there protected. The development of the eggs of 
Fundulus depends on the temperature of the water, but is about three 
weeks in length. 
During development, the hardy eggs of Fundulus heteroclitus 
may be subjected to almost unbelievable maltreatments and still de- 
velop. They will develop in water ranging from distilled to even 
as high as 40 per cent 1 salt. Placed in solutions of alcohol, ether, 
chloretone and magnesium chloride in sea water, many develop ab- 
normally, but develop to hatching. [Stockard (14, 15) ]. 
The young fish hatches with a yolk sac which rapidly disappears, 
leaving it to feed on minute plankton. By the following spring after 
hatching a young Pundulus is ready to eat much the same foods as 
the largest of its kind. 
The worst enemy of the killifish is probably his own kind. Many 
eggs are eaten by the adults of the same species. Among the fish 
known to eat Fundulus helteroclitus are the striped bass, weakfish, 
smelt, blue fish and dogfish. Sea birds and even domestic ducks 
are also known to be enemies of the little killifish, [Bean (1) ]. 
Man takes advantage of the fact that killifishes are easily ob- 
tainable and uses quantities of them as bait for other larger fish. 
Foop oF THE KILLIFISHES 
The very young Fundulus of a little less than a year can eat as 
many as six pupz of the mosquito in half an hour and survive the 
meal. In an experiment performed purely as an extra, I placed a 
very small Fundulus (1em.) in a jar with six pup of Aedes sollici- 
fans Wlk. which were at least half its length. In 30 minutes all the 
pupe were eaten. ‘The first one seized was eaten in about 6 minutes. 
Examinations of the stomachs of adult Punduli showed that they 
eat larve, pups, and adults of all the salt-marsh mosquitoes. ‘They 
also eat Dytiscus, Notonecta and many Daphnids. In the winter 
small quantities of algal matter and a few small shrimps constitute 
the most of the food of the active individuals. In the early fall, the 
chief food besides mosquitoes seems to be insect and snail eggs and 
occasionally a few fish eggs. 
Mr. T. C. Nelson of the University of Wisconsin, informs me 
1From unpublished experiments by the author. 
