SYSTEMS OF RAYS ROUND THE NUCLEUS 253 



exclusively the case at a later period, that is to say, after the 

 two nuclei have become closely apposed, it would not be 

 possible for a system of rays streaming out evenly on all 

 sides to be developed round them ; there would rather have 

 to be two such systems indicated if the radiation was 

 exclusively caused by the centrosomes, as is in fact actually 

 the case in division. I think, therefore, that the nuclei 

 themselves take part in the production of rays, which 

 harmonises well with the fact that the two pronuclei during 

 the formation of the radiating suns grow to a considerable 

 extent, and therefore absorb material from their surround- 

 ings. 



That the nucleus can also cause by itself the formation 

 of a system of rays centred upon it, seems to me from 

 some other facts very probable, even if not certain. I 

 refer especially with regard to this point to the observations 

 of Schewiakoff (1887), which were controlled by me, upon 

 the division of Euglypha. Here, there appears round the 

 nucleus, while passing into the spirema stage, a regular 

 radiate striation on all sides, having nothing to do with 

 the two polar suns, which do not develop until much later, 

 after the first system of rays has disappeared again. Now it 

 is a very suggestive fact, that the nucleus during the exist- 

 ence of this striation increases its volume two or three 

 times, and therefore must take up a considerable quantity of 

 fluid from the surrounding protoplasm. The formation of 

 this system of rays round the strongly growing nucleus of 

 Euglypha again confirms therefore our view of the cause and 

 significance of the striation. It may be not improbable that 

 similar striations appear still oftener round the nucleus. 

 Heuser has seen the same phenomenon round the vegetable 

 nucleus in the spirema stage. I may refer further to the fact 

 that, according to Strassburger's observations, a regular 

 system of rays spreading out on all sides makes its appear- 

 ance during the so-called free cell formation in the embryo 

 sack of Phanerogams, which is to be regarded in just the 

 same manner as the cases described above. 1 



1 Whether the appearance of rays, which Vejdowsky (1888) described 

 round the centrally placed germinal vesicle of the ripe ovum of Rhyn- 



