of Edinburgh, Session 1884-85. 167 
preparatory to its assuming the downward direction characteristic of 
summer. 
It is curious how great a difference there is between the tempera- 
ture of rivers in the same district and apparently under the same 
conditions ; and the only way to arrive at an understanding con- 
cerning it is by having simultaneous observations at different places. 
The basin of the Forth is very poorly supplied with meteorological 
stations, and if anything like thorough knowledge of the physical 
conditions of this river system is to be obtained, such stations must 
be set in action. This could be best done by the assistance and co- 
operation of the proprietors on the banks of the river, who would 
doubtless in time reap practical advantages from the work done. 
I have to thank Mr T. Morton Ritchie, B.Sc., for his valuable 
help in making many of the observations described in this paper; 
various members of the scientific staff of the Scottish Marine 
Station, where the work was carried on ; and in particular the crew 
of the “ Medusa,” without whose care and assistance it would have 
been impossible to do much of the deep-sea work. 
5. The Relations of the Yolk to the Gastrnla in Teleostean 
Embryos. By J. T. Cunningham, B.A. 
[Abstract). 
W In the course of my studies on the development of marine osseous 
fishes, I have recently made at the Scottish Marine Station some 
observations on the living ova of the cod ( Gadus morrhua, L.), 
haddock (6r. ceglefinas , L.), and whiting (6r. merUmgus , L.). The 
eggs of all these species are pelagic ; that is to say, they are not 
adhesive, and are of less specific gravity than the sea water into 
which they are shed by the parent fish, and they consequently 
undergo development at or near the surface of the sea. They float 
at the surface of still sea water in a glass vessel such as was used to 
contain them in the laboratory, and at the surface of the sea in calm 
weather. But if the glass vessel be shaken the eggs are dispersed 
throughout the water within it, and when the surface of the sea is 
agitated by wave motion, a similar effect is produced, the buoyant 
eggs are dispersed through the water to a depth depending on the 
