Abstract
In the complex chain of interrelated processes which make up the early changes in the egg during activation (see Tyler, 1941, 1955; Runnström, 1952; Rothschild, 1956; T. Yamamoto, 1956; Allen, 1958) many phenomena are still unclear : for example, the problem of the fertilization impulse, the rate of its spread, and its relationship with the other changes in the egg; the problem of the origin of the perivitelline space colloid and of its relation to the material of the cortical granules (Runnström, 1952; Rothschild, 1956; Allen, 1958). The main objects of investigation have hitherto been the eggs of sea urchins and, to a lesser extent, of teleost fishes, so that a danger exists that the sequence of phenomena characteristic of these eggs may be supposed to hold generally. Acipenserid eggs, because of certain peculiarities of their structure and development, are a suitable object for studies of this kind.