152 
Experiment No. 23.—March 13th, at 3 p.m., took an egg 
from tray No. 1, where it had been 91 days, and perceived that 
the young was very vigorous. It was placed in a dry tube and 
forgotten until 7.10 p.m., when the ovum was found with its 
upper surface dried, and a saucer-shaped depression which had 
contracted it to about 3 of its normal size. On examining it 
with a magnifying glass the heart of the embryo could be seen 
rapidly but very feebly pulsating. It was at once transferred 
to a wine-glass full of clean water, but it was upwards of half- 
an-hour before the egg had again regained its original shape. 
Next morning it was found to be alive, so fresh water was again 
supplied, and this was continued daily until March 20th, when 
it hatched at 3 p.m., the emtryo emerging in a lively con- 
dition. 
These experiments gave rise to the question, Is it true, as 
generally asserted, that water obtains access to the embryo 
through the porous egg-shell? Or can it be that gases are 
merely transferred from the surrounding water to it through 
the shell? It is perfectly evident that if the egg can live, and 
the young develop in damp moss, that the presence of water is 
not an absolute necessity. Dampness, however, would assist in 
this transfusion, and it is much more easy to suppose that in 
some of the foregoing experiments (where growth has continued 
weeks without water) that gases are simply supplied through 
the egg-shell: and that this absorption does not necessarily occur 
through the micropyle I was also able to assure myself of. 
I removed one egg from an incubating tray, and kept it in the 
air until it was dry and clear. Having divided the shell into 
two halves, and placed a solution of picrocarmine in the half 
that did not possess a micropyle, I found that the colouring 
matter obtained access to the surrounding water through the 
egg-shell. In short respiration is carried on by a simple 
physical law, the shell-membrane permits the transfusion of 
gases and an interchange takes place between the gaseous 
matter on the two sides of the egg shell. 
In investigating, on a small scale, the effects of motion and 
concussion upon the ova of Salmonide, such must be considered 
