BIGELOW: NUCLEAR CYCLE OF GONIONEMUS MURBACH1I. 3G5 



The oocyte nucleolus. — The oocyte nucleolus deserves separate con- 

 sideration on account of its special features. This structure, according to 

 the accounts hitherto published, shows a good deal of variation in differ- 

 ent coelenterates. Thus, in Geryonia (Fol, '73), Eucope (0 Hertwig, 

 '78''), Spongilla (Fiedler, '88), Esperella (H. V. Wilson, '94), Aequorea 

 (Hacker, '92 r, ) ) Tubularia (Doflein, '96), Clava (Harm, : 02), and Gon- 

 otliyrea (Wulfert, :02), the nucleoli of the germinative vesicles are of a 

 single sort, while in other genera, such as Aeginopsis, Nausithoe, Pela- 

 gia, Physophora (0. Hertwig, '78''), Hydra (Brauer, '9l a ), Rhodalia 

 (Montgomery, '98 f ), Cordylophora (Morgenstein, : oi), and Gonionemus, 

 there are two distinct classes of nucleoli which correspond closely in 

 structure and staining reactions to the chief and accessory nucleoli so 

 often described in the germinative vesicles of the higher Metazoa. 



The general characters, and probably the relationships of these two 

 classes of bodies seem, from the published accounts, very similar in the 

 various forms in which they have been observed. But they have been 

 variously interpreted. Thus Flemming ('82) doubts whether there is 

 any valid distinction between the two; Brauer ('9l a ) and Floderus ('96) 

 believe that accessory nucleoli are formed as buds from the chief nucleo- 

 lus ; but Hacker ('93) contends that there is no genetic connection be- 

 tween the two. List ('96) considers somatic and accessory nucleoli more 

 closely related to each other than is either of them to the chief nucleo- 

 lus. Montgomery believes that the two stand in no genetic rela- 

 tion to each other, in support of which view he points out ('98 b , p. 517) 

 the probability that the structure interpreted as an accessory nucleolus 

 in the older accounts was really nothing more than one of the vac- 

 uoles of the chief nucleolus, or extruded vacuolar substance of the 

 latter. 



Eohde's (:03) observations, which are, in the main, supported by the 

 conditions in Gonionemus, have thrown fresh light on this subject. 

 There is, in Bolide's opinion, no more fundamental distinction between 

 chief and accessory nucleoli than there is between the chromatin nucleoli 

 and plasmosomes of somatic cells. On the contrary, the first two struc- 

 tures bear to each other much the same relationship as do the last two. 



During the growth stage of the germinative vesicle both classes of 

 nucleoli are " erythrophile," i. e., combine with acid dyes. But the chief 

 nucleoli originate, just as do ordinary plasmosomes, as nuclein structures, 

 and, therefore, in their younger stages combine with basic dyes. This, 

 however, is not the case with the accessory nucleoli. While the chief 

 nucleoli are formed shortly after the last oogonial division, the latter do 



