HARGITT: PENNARIA TIARELLA AND TUBULARIA CROCEA. 187 
in a different place and manner, no stages having been obtained con- 
necting this with the maturation spindle. In 'Tubularia, the odcytes 
not used as food often remain in contact with the egg, and when de- 
generating they bear so close a resemblance to polar cells as to make it 
almost impossible to distinguish between the two, unless the polar cells 
are still actually joined to the egg. However, what little evidence 
there is favors the view that this nuclear condition in Tubularia is a 
stage immediately preceding the formation of the first polar cell. A 
fragmentation of the nucleus at or before this time, as claimed by 
Allen (:00), does not occur, the polar cells being formed without doubt 
by mitosis. There is no case in which I have not been able to find a 
nucleus of some sort in each egg examined, and never has there been 
the slightest sign of fragmentation. A spindle found close to the sur- 
face of the egg in a nearly radial position (Fig. 51a) may represent the 
first maturation spindle. Centrosomes and asters could not be de- 
tected. While the preservation of this egg was not perfect, it was 
good enough to show the structure of the spindle itself clearly. The 
chromosomes in the equatorial plane, while very small and massed 
together, show a splitting, and the two parts are just beginning to 
separate. The small sphere outside the egg, at the left of the figure, 
may represent a polar cell, but in size and general appearance it is 
more like a degenerate odcyte. In the centre of this egg was found 
another nuclear body (Fig. 51b), which probably represents the sperm 
nucleus. The second maturation spindle was not seen in ‘Tubularia. 
Figure 52 shows the two polar cells, one of which is still joined to the 
egg by interzonal filaments (the body shown with dotted outlines was in 
the section following the one drawn with a continuous outline). The 
two polar cells are equal in size, each contains some cytoplasm, and the 
chromatin is in several masses not surrounded by a membrane. ‘The 
egg nucleus has the form of a single spheroidal vesicle with the chro- 
matin scattered along a reticulum; no asters were present. Figure 
53 shows a nearly tangential section of another egg, provided with two 
polar cells outside the membrane. In this case, too, the chromosomes 
are aggregated into several discrete masses. ‘The egg nucleus occupies 
a superficial position in an elevation of the surface of the egg, and there 
are no cytoplasmic radiations in its vicinity. 
In one case only (Fig. 54) was a spermatozoén found within the egg. 
The sperm head had as yet undergone no marked change. It was 
accompanied by a distinct aster, in which, however, no centrosome 
could be detected, though several stains were used in an attempt to 
demonstrate one. Unfortunately the condition of the egg nucleus 
