38 THE ASTER IN ARTIFICIAL PARTHENOGEIsESIS 



exhibit vacuoles which, instead of being collected in the center of the 

 egg, are scattered throughout the cytoplasm. Radiations appear 

 about these vacuoles with the result that the egg becomes filled with 

 many small asters. The longer the eggs have been left in the hyper- 

 tonic solution the more numerous will be the asters, and most if not 

 all of these asters develop independently of one another. Irregulari- 

 ties may occur, even when the vacuoles collect in the center of the 

 egg. In such cases an apparently normal single aster first results. 

 Upon its disappearance, the central liquid area, instead of flowing 

 away from the center into two polar bodies, produces three or four 

 irregular lobes. About each of these lobes radiations appear in the 

 egg cytoplasm producing a multipolar aster. In one instance one 

 such lobe separated itself from the main body and a complete aster 

 formed about it while a multipolar aster formed about the rest of the 

 hyaline area. When the periphery of a multipolar aster reaches the 

 surface of the egg cleavage furrows form between each lobe of the aster 

 so that such eggs may segment simultaneously into three or four or 

 more blastomeres. Asters which form independently of the central 

 area never seem to be large enough to bring about segmentation of the 

 egg into considerable masses. When such asters lie close to the periph- 

 ery of the egg, furrows often grow in from the surface of the egg enclos- 

 ing the asters. In this way a superficial type of segmentation results 

 with the pinching off of small masses of the egg. The development 

 of cytasters resulting in a spurious segmentation has already been 

 described by Wilson.^ 



The first aster appears at about the same time after the acid treat- 

 ment, irrespective of whether the eggs have been subsequently treated 

 with the hypertonic solution or not. However, with subsequent 

 hypertonic treatment, the reappearance of the radiations following 

 the fading away of the first aster occurs about more than one center. 

 This results in segmentation of the egg. The reaction, therefore, 

 which is peculiar to hypertonic treatment shows up only after the 

 disappearance of the first aster. At that time the persisting central 

 liquid area of the aster, instead of remaining as a single centralized 

 mass, separates into two or more bodies with the result that the 

 following reappearance of rays in the cytoplasm occurs as radiations 

 about these bodies. This produces multiple asters. If there be 



