116 



THE AMERICAN NATURALIST [Vol. L 



chromatin-grains, producing a granular nucleus of the 

 type seen in Dinoflagellates, in Haemogregarines, and in 

 Diatoms. Amongst the chromatin-grains there may be 

 present also one or more grains or masses of plastin 

 forming true nucleoli. At the opposite extreme a clump 

 of chromatin-grains becomes firmly welded together into 

 a single mass in which the individual grains can no longer 

 be distinguished, forming a so-called karyosome, consist- 

 ing of a basis of plastin cementing or imbedding the 

 chromatin-grains into a mass of homogeneous appear- 

 ance. Whatever the type of nucleus formed, the concen- 

 tration of the chromidia into nuclei does not necessarily 

 involve all the chromidia, many of which may remain free 

 in the cytoplasm. 



In the chromidial condition the chromatin-grains scat- 

 tered in the cytoplasm are lodged at the nodes of the alve- 

 olar framework. 24 Consequently a supporting framework 

 of cytoplasmic origin, the foundation of the linin-frame- 

 work, was probably a primary constituent of the cell- 

 nucleus from the first. In many nuclei of the karyoso- 

 matic type it is very difficult to make out anything of the 

 nature of a framework, which, however, in other cases is 

 seen clearly as delicate strands radiating from the kary- 

 osome to the wall of the vacuole in which the karyosome 

 is suspended. Probably such a framework is present in 

 all cases, and each supporting strand is to be interpreted 

 as the optical section of the partition between two proto- 

 plasmic alveoli. 



With the formation of the nucleus the cytode or pseudo- 

 moneral stage has become a true cell of the simplest type, 

 for which I propose the term protocyte. It is now the 

 starting-point of an infinite series of further complica- 

 tions and elaborations in many directions. It is clearly 



24 Cf. Dobell, "Observations on the Life-History of Cienkowski's Arach- 

 nula," Arch. ZVm/-V, ml mul, . XXXI (1913), p. 322. The author finds that 



to form a vesicular nucleus. Since the fully-formed nucleus contains nu- 

 merous grains of chromatin, the original chromidiosome must multiply in 



