But the difficulty in accepting this conclusion was that there was a distinct though gentle respiratory movement of the jaws and Opercula; and if the pumping of the water from beneath the body caused a negative pressure there, and a positive pressure on the outer side of the body, it seemed equally certain that the respiratory movement must force water into the space beneath the body and so cause a positive pressure there which would tend to force the fish away from the surface with which it was in contact.
"Hormones and Heredity"
J. T. Cunningham
I have repeated Gudernatsch's experiment with the following results:- This year I had a considerable number of tadpoles of the common English frog, which were hatched between March 26 and March 29. On April 12, when they had all passed the stage of external gills and developed internal gills and Opercula, I divided them into two lots, one in a shallow pie-dish, the other in a glass cylinder.
"Hormones and Heredity"
J. T. Cunningham
The tails were only half the original length, all had well-developed hind-legs, some with toes, but the fore-legs were beneath the Opercula, not projecting from the surface.
"Hormones and Heredity"
J. T. Cunningham