RELATIONS OF YOLK TO GASTRULA IN TELEOSTEANS. 3 
piscatorius was plentiful but not ripe; Trigla gurnardus, 
Pleuronectes limanda, P. microcephalus, and Hippo- 
glossoides limandoides were also unripe; Pleuronectes 
platessa was spent. 
The fertilised eggs were brought to the Marine Station on 
the morning of March 31st, and transferred to clean water in a 
number of vessels. The eggs were removed by skimming them 
with a spoon from the surface of the water, where they floated 
when undisturbed. They still floated at the surface when 
placed in the sea-water of the station, although its density is less 
than that at the Isle of May; the sp. gr. of the latter at 15°6° 
C. as compared with pure water at 4° C. is 1:025, of the former 
1:023. The water in which the eggs were was changed from 
time to time, usually once in two days; this was sometimes 
effected by carefully siphoning off the water without disturbing 
the eggs at the surface, and then replenishing the vessels with 
clean water. Sometimes, when there were a large number of 
dead eggs at the bottom of a vessel the living ones were trans- 
ferred by means of a spoon to another vessel full of clean water. 
One of the vessels was aérated with a stream of air-bubbles 
from a small aérating apparatus, but the eggs in this did not 
thrive any better than those treated solely by the method of 
transference. 
On April 3rd, in addition to a new supply of the three kinds of 
ova before obtained, some eggs of the grey gurnard (Trigla 
gurnardus, L.) were brought to me. These floated at the sur- 
face of the water in which they were carried, and were treated in 
the same way as the others, but they immediately sank to the 
bottom when placed in the water of the station. Thus their spe- 
cific gravity is greater than that of the station water and less than 
that of the sea water at the mouth ofthe Forth. It lies between 
1-023 and 1:025, while that of the ova of the three species of 
Gadus is less than 1:023. 
