6o4 GRIFFIN. [Vol. XV. 



erates in the cytoplasm (PI. XXXI, Figs. lo, ii). The source 

 and mode of growth of this reticulum are impossible to deter- 

 mine. It evidently does not arise through an anastomosing of 

 chromosome processes as in the germinal vesicle of Pristinrus 

 (Rtickert, '92) and epithelial cells of Salamander (Rabl, '85) ; 

 for all the facts suggest that its development is independent of 

 the chromosomes which are passive during its growth. I would 

 conclude, therefore, that this nuclear reticulum is a secondary 

 and special structure, developed to preside over the metabolic 

 functions of the egg during the growth period, when the true 

 chromatin (idioplasm), in the form of chromosomes, is passively 

 awaiting the formation of the spindle. ^ This view may be 

 elucidated by a comparison with the Infusorian nuclei. It is 

 here generally conceded that the macronucleus is the more 

 especially concerned with the purely vegetative functions of 

 the animal, while the micronucleus represents a reserve idio- 

 plasm especially concerned with reproduction. Exactly such a 

 difference in function I conceive to exist between the nuclear 

 reticulum and the chromosomes in ova of the Thalassema type. 

 The following rough parallel may be drawn : 



Infusorian. Egg-Cell. 



1. Vegetative period, when the cell is Growth period, presided over by the 

 dominated by the Macroniicletts. mtclear reticulum, 



2. Macronucleus breaks up, disap- Nuclear reticulum breaks up, disap 

 pears, to be followed by pears, to be followed by 



3. Division and persistence of Micro- Division and persistence of the Chro 

 nucleus. mosomes (polar mitosis). 



Up to this stage my results on the tetrad-formation agree 

 with those of vom Rath in Gryllotalpa. Instead, however, of 

 immediately concentrating into tetrads, as in Gryllotalpa, the 

 rings now begin to elongate, and their granular composition 

 becomes very apparent. In full-grown ova within the sexual 

 pouches they appear as small, much-coiled, or zigzag, granular 

 rods (PI. XXXI, Fig. 6), generally near the membrane, though 

 sometimes a few are more nearly central. This coiled or zig- 



^ In the Selachians it would appear (Riickert, '92) that its function is assumed 

 by the true chromatin, a similar reticulum arising by the chromosomes putting 

 forth anastomosing processes, and losing their affinity for chromatin stains. 



