BIGELOW : NUCLEAE CYCLE OF GONIONEMUS MURBACHII. 363 



Nucleoli of the compound t}'pe which occurs in these two coelenterates 

 have been described in a few cases among tbe higher Metazoa. Thus, 

 they are characteristic of leucocytes (Heidenhain, '92, '94), of epidermal 

 cells of larval salamanders (Lavdovsky, '94), and of certain mammalian 

 ganglion cells, gasteropod ganglion cells, and young ova of amphibians 

 (Rohde, : 03), and especially of the spermatogonia of Paludina (Auer- 

 bach, '96). This last example shows a particularly close parallel to the 

 condition in Gonionemus, since, according to Auerbach, the nucleolus, 

 when treated with the Auerbach mixture of acid fuchsin and methyl 

 green, shows a peripheral shell stained green and a central mass stained 

 red. The similarity is still further emphasized by the fact that in Palu- 

 dina, as in Gonionemus, the "shell" disintegrates during the prophase, 

 and contributes to the formation of the chromatin reticulum. Such 

 cases as these have led even Montgomery ('98 b , p. 507) to admit that 

 " it would seem probable that the nucleolus in some cases has an en- 

 velope of chromatin forming a distinct capsule separated from the chro- 

 matin network of the nucleus." Yet he seems to have overlooked this 

 as evidence of the relationship of nucleoli to other nuclear elements ; 

 for he states that he is unacquainted with any observations " which show 

 that the nucleoli derive any part of their substance from the chromatin " 

 (Montgomery, '98 b , p. 523). 



Light has been thrown on this question by Rohde (: 03), whose meth- 

 ods, based on the use of basic-acid combinations of coal-tar stains, were 

 much more precise than those of most of his predecessors. Ail nucle- 

 oli, says Rohde (:03), originate within the nucleus. Furthermore, nuclei 

 of all kinds originate by a concentration of nuclein — or chromatin — ■ 

 granules, and in their young stages exhibit an affinity for basic dyes. 

 This is true of plasmosomes as well as of chromatin nucleoli : a fact 

 which Rohde was able to establish by an extended series of observations. 

 There is, then, as Flemming ('82) long ago surmised, no fundamental 

 difference between the two classes of nucleoli, and instead of there being 

 no genetic connection, as Montgomery ('98 b ) maintains, the relationship 

 is of the closest, for plasmosomes are descended from chromatin nucleoli 

 by a gradual alteration of their substance. Compound nucleoli, such 

 as those mentioned above, which show a differentiation of their sub- 

 stance into an outer chromatin layer and an inner plasmatic mass, are 

 nothing more than intermediate stages in the formation of plasmosomes. 

 Such intermediate stages may, however, be permanent, as we have seen 

 that they are in the case of Gonionemus. We have also seen that, in 

 this form, the compound nucleoli are descended from nuclear elements 



