MUSEUM OF COMPARATIVE ZOOLOGY. 93 
I was at the Fish Commission Laboratory, and for his kind co-operation 
in securing embryological material both at Gloucester and at Wood’s 
Holl, Massachusetts. 
II. PRELIMINARY Account. 
(a) The Material. — The material upon which the following observa- 
tions are based is from Fundulus heteroclitus, an oviparous Cyprinodont, 
known in common parlance among fishermen as the “Short Minnow.” 
The material was secured during the month of July, 1889, at Wood’s 
Holl. The adult fishes of both sexes were taken with a seine along the 
shores of Buzzard’s Bay, and confined in the aquaria of the hatchery 
at the Fish Commission station. At the proper time the ripe ova and 
sperm were taken by the process known as “stripping,” and the ova 
were “artificially” fertilized and kept in running sea-water in a labo- 
ratory aquarium. From this supply of ova small quantities were 
taken at intervals up to the time of hatching, which varies from six- 
teen to eighteen days after fertilization, the temperature of the water 
being at an average of about 20° C. 
The ova are submersal, remaining at the bottom of the aquarium, 
unless the current is strong enough to agitate the water sufficiently to 
raise them. ‘They are covered with fine filaments, which are produced, 
according to Eigenmann (’90, pp. 129-132), by a membrane lying outside 
the zona radiata. The filaments of different eggs become entangled, 
and hold the eggs in clusters. The ova are about 2mm. in diameter, 
with considerable variation in ova taken from different females. They 
are somewhat translucent, contain numerous oil globules, which are at 
first near the blastodise, but are gradually carried over the yolk during 
the course of the development of the blastodisc. In Fundulus the yolk 
is not all absorbed until several days after hatching. 
(b) The Technique employed. — The ova were killed at intervals in- 
creasing from one hour in the younger to eight hours in the older stages. 
The killing reagents used were Perenyi’s fluid, Kleinenberg’s picro- 
sulphuric mixture, and a solution of 0.25% osmic acid, followed by 
Whitman’s modification of Merkel’s fluid. The osmic material was 
washed in water, both before and after the use of Merkel’s fluid, and 
all the material subsequent to the use of the killing reagent was car- 
ried through grades of alcohol to 90%. The material preserved with 
Perenyi's fluid has proved to be the most satisfactory, especially with 
the younger stages, but Kleinenberg’s picro-sulphurie mixture is per- 
haps rather better for the more advanced stages. Both these reagents 
