THE OVUM IN THE AMPHIBIA. 
235 
No. 2. Fifty-eight ova were treated in exactly the same way, the interval being 
^honijfteen seconds, and the whole time sixty. 
The seminal fluid employed was obtained from two males, the fluid used toNo.2 being 
from a male which had paired four days before. Out of the whole number of eggs in 
the two sets, amounting to one hundred and thirty-four, not one produced an embryo. 
No. 3. March 30, 1850. p.m. 5^' 5“. Atmosphere 49° Fahr. 
One hundred and eight ova were passed on a moist surface, and were immediately 
bathed with a thick solution of gum as above, and one second afterwards with seminal 
fluid in water ; the whole time occupied being sixty seconds. 
Segmentation took place in two, or at most only three of these ova, and even in 
them very imperfectly, and much slower than in the corresponding ova of the set to 
which they belonged, Set Q (p. 228-9), in which the fluid employed was obtained 
from the testes of the Frog, and regarded as immature. 
No. 4. P.M. 5^ 18*". — Fifty-eight ova passed on moistened surface were immediately 
bathed with solution of gum, and one second afterwards with seminal fluid from the 
same male as No. 3. The whole time occupied was forty-five seconds. 
The result of these two experiments, as compared with others of the set to which 
they belonged, Set Q, was exceedingly curious. In the experiments with the nitrate 
of potass as in Q 7, segmentation was carried to some extent, and the divisions of 
the yelk were multiplied; while only four ova out of the fifty-eight, in this with gum, 
gave any evidence of segmentation, and the process was not advanced further, either 
in this or in the preceding experiment. No. 3, than to the completion of the primary 
division of the yelk into two hemispheres. Thus not only was the process entirely 
prevented in the great majority of the ova, but it was also very much retarded in 
those in which it did take place, and this simply, as it appeared, by the mechanical 
hindrance of the gum. Could it be that the effect was produced on the endosmic 
action of the yelk ? These trials certainly appeared to show that the obstruction 
was a mechanical one. 1 need scarcely remark, that no embryo was produced in 
either of these experiments. 
No. 5. April 3, 1850. p.m. 3^ 25"*. Atmosphere 60° Fahr. 
Sixty-one ova were passed on a moistened surface and were immediately bathed with 
hnpregnating fluid, and two seconds afterwards with a thick solution of gum-arabic, 
and water was then added ; the whole time occupied being only twenty seconds. 
This experiment, when compared either with the four preceding ones, made at a 
temperature of the atmosphere eleven degrees lower, or with that which follows. 
No. 6, seems to point to the exact nature of the operation of the gum. At four hours 
and five minutes from fifteen to twenty ova had become segmented, and others were 
in the act of becoming so. At seven hours and a half more than one-half of the 
whole number had changed, and were perfectly healthy. Thus, in this case, in which 
the gum was applied after the seminal fluid, impregnation occurred earlier than in 
corresponding experiments of the same set, R 6, 7 and 8, with nitrate of potass, when 
it happened in from four hours, and fourteen to twenty minutes. It was even as 
2 H 2 
