468 
DE. W. H. EANSOM OIST THE OVUM OE OSSEOUS FISHES. 
previous paper it was said to have no effect on the yelk contractions. I used then a 
single cell containing j/' of gold wire, and the same of zinc, excited by a solution of 
chloride of sodium. A like negative result was obtained, with reference to the cleavage, 
while using a cell containing carbon and zinc, each 2 square inches, excited by common 
salt. 
Later experiments in May 1864 with more powerful currents and better appliances 
have reversed the result. 
I used an induction apparatus made by Stqehree, which admits of nice graduation, 
and has as much power as is usually required for medical purposes. 
A cell was prepared, the idea for which had been suggested by Kuhne *, of sufficient 
depth to permit the eggs to be covered, without pressure, and the conductors were so 
suspended that the movements of the stage of the microscope were unimpeded. A 
contact breaker was introduced into the circuit, so that it could be closed for any 
required time without touching the stage or removing the eye from the microscope. 
A very weak secondary current was employed, using only j>" of metallic contact, and 
pushing the coil as far off the core as possible ; the shocks were then barely felt by the 
moistened fingers. The primary current was found to be less suitable for these experi- 
ments, being less perfectly graduated. 
An egg, fifteen minutes after impregnation, was placed between the poles in the cell, 
and watched for a minute or two with a power of X 75. The yelk was seen to be lan- 
guidly changing its form, by flattening one segment ; no travelling waves were present 
(Plate XVII. fig. 59). On then making contact for about ^ minute, there appeared, 
after a very brief interval, which I could not accurately measure, a deep notch surrounded 
by radial foldings of the inner sac in that part of the yelk-ball nearest to the platinode 
(Plate XVII. fig. 60). The tardiness of this reaction made it impossible to note the 
relative effect of making and breaking contact. 
After another similar application of the current, another notch formed near the 
first, and directly after, the inner sac burst at a point distant from the notch, and the 
food-yelk escaped (Plate XVII. fig. 61). 
Other applications of the current were followed by indentation of the yelk, on the side 
opposite to the first formed one, and the inner sac burst near the new indents; the 
escaping food-yelk showed signs of chemical change, being very granular from electro- 
lysis (Plate XVII. fig. 62). 
These excited contractions were followed by oscillations. 
At the rupture in the inner sac the torn edge is well seen, as it retreats during the 
shrinking of the yelk-ball ; it is often folded and ragged, sometimes drawn into threads. 
The circuit being again closed as before, the inner sac shrunk into a lobular mass, 
which contained the greater part of the formative yelk, and a little food-yelk, which was 
seen to escape more rapidly under the influence of the current. Electrolysis was more 
marked in the yelk of both kinds (Plate XVIII. fig. 63). After this stage repeated 
* Untcrsucliungen iiber das Protoplasms nnd die Contractilitat, 1864, p. 147. 
