2 
J. T. CUNNINGHAM. 
carefully examined as many successive stages in the living 
condition as time would allow, and preserved specimens at 
frequent intervals. These preserved examples I have since 
studied by means of section-cutting in the laboratory of the 
Scottish Marine Station. 
My embryos were preserved by two methods. Some were 
placed fresh in a saturated solution of corrosive sublimate, 
others in weak solutions of chromic acid, generally about 
£ per cent. In either case spirit was substituted after a 
short time for the fixing solution. Neither of these methods 
is perfectly satisfactory ; the corrosive sublimate leaves the 
embryos in too soft a condition, so that it is difficult to extract 
them from the vitelline envelope and put them through the 
processes of staining and embedding, without breaking them. 
On the other hand, when sections are successfully cut they are 
found to be satisfactorily stained and to show well the relations 
of the layers. The embryos treated with chromic acid are very 
hard and easy to manipulate, with the exception that the yolk 
in cutting often breaks the other parts ; but these embryos are 
very refractory towards staining fluids, and the colouring of 
the sections is never as differential as one would wish. Never- 
theless, although my sections are not quite perfect in all 
respects I have been able to make out a good deal as to the 
development of the various organs. The following account 
refers chiefly to the origin of the intestine, but I hope to clear 
up some other points later. It is scarcely necessary to add 
that my sections were cut with the microtome of Jung, by 
means of the method perfected by Giesbrecht. 
It is well known that the rate of development in herrings’ 
ova depends largely on temperature. I shall not here discuss 
the various experimental data of this part of the subject, but 
merely state the temperature to which my specimens were 
exposed, and the period at which the chief stages were reached. 
The first eggs I obtained were fertilized at 4.30 a.m., August 
14th ; the temperature of the surface of the sea at the time 
was 133° C . ; the temperature of the water where the eggs 
were kept varied from 11-5° C. to 145° C. These eggs began 
