238 HILL. [Vows IX. 
In what follows the description of Salmo 7 mm. in length is 
based on the study of living embryos, but has been verified and 
extended by the examination of sections. In older stages the 
presence of pigment prevented a study of the living embryo, 
and the descriptions are therefore based altogether on sections. 
The description of the organ in other Telosts is taken from 
living embryos, while in Amia it is again based exclusively 
on sections. 
As a fixing reagent, Flemming’s stronger solution was found 
to give satisfactory histological results. In older stages, in 
order to secure a better penetration of the fixing fluid and 
in order to overcome the difficulty of cutting the lens, the 
lateral eyes were removed and only the dorsal part of the 
head immersed in Flemming’s fluid. This part was subse- 
quently stained in toto in carminic acid and then sectioned 
in paraffin. In order to give the nerve fibres a deeper stain 
the sections, after being fixed on the slide, were immersed 
for twenty-four hours in saturated carminic acid in 80% 
alcohol kept at a temperature of 45° C. 
In the study of living embryos the egg membranes were 
always removed. A piece of fine copper wire about two 
inches in length was twisted into a loop, the diameter of 
which was a little less than the diameter of the yolk sac of 
the embryo. The ends of the wire were then bent in such 
a way that they formed a support for the loop so that when 
placed in a flat dish filled with water the loop was raised 
I or 2 mm. from the bottom of the dish. The embryo was 
taken into a wide-mouthed pipette, held in a vertical position, 
and forced into the loop tail foremost in such a way that the 
loop, by constricting the yolk sac, held the embryo firmly in 
position. By bending the wire supporting the loop the embryo 
could be brought into any desired position, and any view of 
the head could be obtained. 
I desire here to acknowledge my indebtedness to the United 
States Commissioner of Fish and Fisheries who on several 
occasions has had sent to me a very liberal supply of Salmo 
material. JI am under equal obligations to the Michigan Fish 
Commission for a supply of Coregonus and Stizostedion eggs. 
