\ CHROMOSOME STRUCTURE 177 



\ ... 



not metachromatin, and has no properties in common witli this 



substance, beyond the fact of affinity for intravitam dyes. Tlie 

 colloidal substances in the vacuoles of flowering plants differ 

 widely in different cases, but they are for the most part composed 

 of alcohol-soluble proteins, tannins and anthocyanins. In matur- 

 ing seeds the vacuoles are alleged to be changed into aleurone 

 grains. These vacuoles, which are at first composed of a weak 

 solution of colloidal protein ^ are then dehydrated and break down 

 into smaller vacuoles, and these ultimately shrink into small 

 solid protein or aleurone grains. At the onset of germination 

 the reverse changes occur : the grains absorb water, swell 

 into small vacuoles, and finally fuse and form larger vacuoles. 

 Unlike Dangeard, however, Guilliermond held the opinion that in 

 certain cases vacuoles may and do arise de novo. He also put 

 forward the suggestion that the Golgi apparatus of the animal 

 cytologist and the Holmgren canals are two pictures demonstrated 

 by different techniques, the one a negative and the other a positive 

 of the same cell structure, which is actually the vacuome demon- 

 strated in the living cells of plants with his neutral red technique. 



THE STRUCTURE OF CHROMOSOMES 



A number of contentious points are involved in a discussion of 

 this nature. The question of correct fixation of material plays a 

 very important part, and no doubt the various views that have 

 been put forward from time to time are due to the fact that 

 different workers have employed varying methods of fixation. 

 Nuclei with large chromosomes have been principally investigated 

 with regard to structure, and it is mainly with these that the 

 following discussion is concerned. 



At the prophase of mitosis the reticulum breaks down into the 

 long slender thread of the spireme and the longitudinal split is 

 first observed. The origin of this split is still a matter of con- 

 troversy. According to Farmer, Digby, Eraser, Newton and 

 others, it arises in the previous telophase, whereas according to 

 Sharp there is no longitudinal split at telophase, but only alveola- 

 tion of the chromosomes to form the reticulum of the new nucleus. 

 Sharp observed the presence of alveoles or achromatic areas in the 



