Electron micrographs of the amphiaster in the whitefish blastula (Coregonus cluperformis)

Abstract

NINE FIGURESThe architecture of the amphiaster has been and still remains an important problem in cytology. This is due, in part, to the fact that the elements of the aster and spindle cannot be clearly seen in most living cells. Accordingly, the fibrous appearance of the amphiaster often obsei-ved in fixed and stained preparations has been held as due to artifact induced by the fixation process. (For discussion of this point see Wilson, '37 and Fry-Wyssling, '48.) On the other hand, considerable evidence has recently accumulated to show that in certain living cells a typical, fibrous appearance of the spindle and asters are present (Cleveland, '35). I n addition, Schmidt ( '36a, b), as well as others, have conclusively shown that both the components of the spindle and those of the aster, under polarized light, show birefringence in their long axis which means that they are composed of paralmlel oriented protein molecules. Other evidence derived from centrifuging and treatment with hypertonic solutions support the classical concept concerning the reality of the fibrous nature of the spindle and asters. Such evidence has led Schrader ('44) to