BIGELOW: NUCLEAR CYCLE OF GONIONEMUS MURBACHII. 361 



of conclusions which have formed the basis of all more recent studies 

 along this line. Not only, says Mathews ('98), do basic dyes combine 

 with chromatin, but they combine as readily, in acid solutions, with any 

 other cell element whatever consisting of an organic acid in combination 

 with a strong base : therefore, since there are many such combinations, 

 e. g., nuclein, hyaline cartilage, and mucin, similarity of staining is no 

 proof of genetic relationship. And from this we must admit that "all 

 conclusions in regard to the origin of cytoplasmic elements from 

 chromatin, or their similarity to chromatin, based on staining reactions, 

 are hence worth very little." (Mathews, '98, p. 452). 



No doubt we must keep this warning constantly in mind in studying 

 the cell as a whole ; but in studying the nucleus alone, carefully chosen 

 tests with acid and basic stains afford far the best iudex to the condi- 

 tion of nuclear elements which we can as yet command. 



Although there occur two types of chromatin, as indicated by their 

 sharply distinct staining reactions, yet, as Heidenhain ('90, '92) first 

 showed, and as has since been thoroughly established, these two are mor- 

 phologically indistinguishable. Nor is their chemical distinction perma- 

 nent, for either one may become transformed into the other, such a 

 change being exactly what takes place in Gonionemus during the regres- 

 sive metamorphosis of the nucleus after division. E. B. Wilson (:00) has 

 emphasized the relation between this change in staining reaction of chro- 

 matin and the periodic changes in its staining intensity, concluding from 

 the very general occurrence of the latter that " the chromatin passes 

 through a certain cycle in the life of the cell, the percentage of 

 albumin, or albumin radicals, increasing during the vegetative activity 

 of the nucleus ; decreasing in its reproductive phase " (E. B. Wilson, : 00, 

 p. 340). More recently Rohde (: 03) has brought abundant evidence 

 to show that this conclusion is correct. 



One feature of this cycle, briefly mentioned by Rohde (: 03), still 

 needs emphasis : this is, that a close correlation occurs between the 

 degree to which the vegetative changes take place, and the degree of 

 concentration of the chromatin. Rohde (: 03) has shown that although 

 an alteration in staining is very general, the degree to which this altera- 

 tion progresses varies greatly in different nuclei. Thus, while in many 

 nuclei, e. g., those of oocytes, vertebrate ganglion cells, and cells of the 

 vertebrate pancreas, it progresses so far that reversal of staining reaction 

 ensues, in others, such as ganglion cells of gasteropods, marrow cells of 

 vertebrates, leucocytes, and gland cells in general, it is so limited that 

 the chromatin structures continue to exhibit an affinity for basic stains. 



