ABSTRACT
The formation of blastomeres by the newly fertilized egg has been studied by many authors, who have found the process a convenient avenue for attacking the general problem of cell division. By far the greater part of the work has been carried out on the eggs of marine invertebrates, and, in spite of their great suitability for most types of experimental embryological investigation, the eggs of Amphibia have not as yet been made much use of in this connexion. The nuclear phenomena attendant on fertilization and cleavage in the Amphibia have been rather fully described (see, for instance, Fankhauser & Moore, 1941), but a short note by Schechtman (1937) contains almost everything that we know about the cleavage of the cytoplasm, and the part played in it by cortical movements.
During the last two summers a few experiments have been made which show that the amphibian egg provides very favourable material for a direct attack on certain of the crucial problems of cell division, since not only is it rather easy to perform micro-surgical operations on the developing cleavage furrow in a manner which would be very difficult in the small eggs of most invertebrates, but the pigmentation of the surface allows the cortical movements to be followed precisely in time-lapse cinema films. These experimental opportunities have not yet been by any means fully exploited, but the preliminary experiments have already yielded certain results which it seems worth while to record.
The experiments were made with eggs of Triturus alpestris which were laid and fertilized normally in the aquarium. The eggs were observed in Holtfreter solution, either of normal strength, or diluted with an equal volume of distilled water.
