278 M. M. Mercar 
The uninucleated condition is reached by suppressing one nuclear 
division while the body divides. There is at no time any such 
degeneration of nuclei as NERESHEIMER has described for O. ranarum 
and O. dimidiata, nor is there any formation of new nuclei from 
chromidia in the cytoplasm. The old nuclei discharge a portion of 
their chromatin and themselves persist as the reproductive nuclei. 
Extrusion of vegetative chromatin. 
In living nuclei, at this stage, which are getting rid of a part 
of their chromatin in this peculiar manner, one observes two large 
balls or discs which by staining are clearly shown to be composed 
of chromatin (Figs. 121—139, Pl. XXII; 236, Pl. XXV). Occasionally 
instead of two such chromatin spheres one finds three (Figs. 132, 
134, Pl. XXII), one or two of these being smaller. In other cases 
but one sphere is found, but in these cases another may have been 
present and have been extruded. The rest of the contents of the 
nucleus lies in the form of granules, generally in an _ hour-glass- 
shaped group, transversely, between the two chromatin spheres when 
two are present (Fig. 121). In the nuclei of the cysts one finds 
sometimes one (Figs. 131, 135, 138, 139, Pl. XXIT; 236, Pl. XXV), 
sometimes two (Figs. 136, 157, Pl. XXII), sometimes three (Figs. 132, 
134, Pl. XXII) such chromatin spheres. In the animals hatched 
from the cysts one finds usually but one such compact sphere of 
chromatin, or often none, the granules remaining in the nucleus 
being often also gathered into a spherical group, which however in 
both the living animals and in acetic carmine preparations can be 
distinguished from the denser sphere. When stained with DeEwa- 
FIELD’s haematoxylin the difference between the two is very clearly 
seen (Figs. 136, 137, Pl. XXII). By the time the gametes are ready 
for copulation, the dense chromatin spheres have entirely disappeared 
from their nuclei (Figs. 148—152, Pl. XXII; 168, 173, Pl. XXIII, 
also Pl. XXIV). 
These compact spheres of chromatin are extruded from the 
nucleus into the cytoplasm and there degenerate. I have studied 
but little the minute animals in the rectum of the frog, before their 
encystment, and have but twice found in them the extrusion of the 
first chromatin sphere (Fig. 124, Pl. XXII; 279 [0. dimidiatal, 
Pl. XX VII); I think, though, this usually occurs at this stage, as 
NERESHEIMER has said. In the cysts (Fig. 253, Pl. XX VI, O. caudata), 
and in young forms hatched from the cysts in the rectum of the 
tadpole (Fig. 143, Pl. XXII, and O. dimidiata, Pl. XXVIII, Figs. 306, 
