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THE AMERICAN NATURALIST [Vol. XLIX 



respectively. Investigations on another fern, Lastrea, did 

 not corroborate these results, however, in one variety the 

 chromosomes being more numerous and the cells smaller 

 than in the parent type. 



Gates by comparing nuclei and cells of different tissues 

 of (Enothera La march in iia and similar structures in its 

 "mutant" 0. gigas with double the number of chromo- 

 somes, found that the 0. gigas cells and nuclei were always 

 larger, varying from a comparative ratio of 1 : 1.5 to 1 : 3. 

 At the same time, it would hardly be wise to maintain that 

 this is always the case, for only a few individuals were 

 investigated. 



Primula sinensis has two forms in cultivation, similar 

 except as to size. The giant form has flowers about one 

 and one half times the size of those produced by the ordi- 

 nary form. Gregory investigated these two forms cyto- 

 logically to determine the cause of this increase. The 

 nuclei and the chromosomes of the giant form were a little 

 larger, though the difference was hardly a measurable one. 

 The chromosome number was the same in both the forms. 

 In a later investigation he has found that some exceed- 

 ingly large plants with nuclei distinctly larger than those 

 of the normal form had double the number of chromo- 

 somes normal to the species. 



Boveri investigated this same relation of cells and nu- 

 clei to chromosome number in N, 2N and 4N larvae of the 

 sea urchin. From these studies, he concludes that chro- 

 matin is non-regulatory, and in the case of decrease, un- 

 regenerable, the cytoplasm in contrast showing the fullest 

 regulatory activity. Further, the size of the larval cells 

 is governed by the chromosome mass and the cell volume 

 is directly proportional to the chromosome number. On 

 the other hand, Conklin's investigations on annelids, mol- 

 lusks and ascidians lead him to take a position opposed 

 to that of Boveri. He says : 



The size of the nucleus, centrosomes and chromosomes is dependent 

 upon the volume of the cytoplasm is clearly shown in Crepidula, where 



