6 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
III. Methods. 
The killing fluids used were (1) 10% formol, (2) Flemming’s stronger 
fluid, (3) Vom Rath’s picro-sublimate mixture, (4) bichromate of po- 
tassium, (5) Gilson’s fluid, arranged in the order of their value. I failed 
to get successful preparations with Vom. Rath’s platinic chloride mix- 
ture. Where decalcification was necessary Flemming’s mixture gave 
very good results. The usual methods of further procedure for sections 
by the paraffin process were used. Heidenhain’s iron hematoxylin gave 
the best stain, though Delafield’s and Ehrlich’s hematoxylins also gave 
successful preparations. These were followed by Congo red or acid 
fuchsin to differentiate fibre tracts. The acid fuchsin has the further 
advantage that it stains developing bone and fibrous connective tissue. 
The Weigert stain with copper and the Weigert-Pal method were both 
used in nerve study. Both adult brains and the larve proved to be 
refractory material for the Golgi method. The rapid method was used, 
but not more than 5 per cent of the specimens gave any impregnation 
whatever. A sojourn of three days in the Golgi fluid and more than 
two in the silver bath were found to give the most successful prepara- 
tions. Material was left in the silver until wanted for sectioning, 
though much of it was sectioned after an exposure of two days to the 
silver nitrate. 
IV. Migration of the Eye and Changes in the 
Cartilaginous Skull. 
Before proceeding to describe the conditions which I have found in 
Pseudopleuronectes americanus, I shall give a brief account of the main 
results reached by previous observers, omitting for the present those of 
Pfeffer. 
1. SumMARY oF PREVIOUS STUDIES ON THE MIGRATION 
OF THE [YE. 
It was suggested about the middle of the last century, that the Pleu- 
ronectide, though unsymmetrical as adults, are, in their young stages, 
bilateral animals like other fish. The brief accounts of Van Beneden 
(53) and Malm (’54), who found young fish quite similar in markings 
to adult flatfishes, but with eyes in a different position, seemed to indi- 
cate the possibility that one of the eyes migrated around the head from 
one side to the other. 
