1896. ] NEW YORK ACADEMY OF SCIENCES. 167 
pole to pole. (Fig. 6.) During the divergence of the centro- 
somes no trace of connecting spindle fibers is to be detected, 
and the interior of the elongating centrosphere appears un- 
changed. The appearance of spindle fibers passing from pole to 
pole, and the disappearance of the intermediate rays mark the 
establishment of the second polar spindle, the dyad chromo- 
somes still, however, retaining their peripheral position. As 
yet no well defined area or centrosphere has appeared about 
each daughter centrosome, but the rays seem to converge di- 
rectly to the centrosomes. Before or during rotation the dyad 
groups become arranged equatorially about the new spindle, 
while an extremely minute centrosphere differentiates about 
each centrosome. The spindle, which at first lay tangentially, 
7. e., With the axis perpendicular to the egg radius, finally ro- 
tates into a radial position lying near the periphery. (Fig. 8.) 
It closely resembles in general appearance the first polar spin- 
dle, but is only one-half the size of the latter and the centro- 
spheres are excessively minute. The curving of the rays, so 
noticeable in the first polar spindle, is here scarcely perceptible. 
In all essential features the subsequent stages are a repetition 
of the first polar anaphase. The second polar body is formed 
at or extremely near the point at which the first was expelled, 
since not only do the two in later stages lie in contact, but in 
several cases the extruding second polar globule was seen to push 
the first before it. ‘Che subsequent history of the polar bodies I 
have not as yet followed out in detail. The first in several 
cases was seen undergoing mitotic division, They persist until 
the second cleavage when they seem to be taken up bodily into 
the egg and absorbed by the cytoplasm, 
The origin of the centrosome of the second polar spindle by 
division of the centrosome of the first has been observed in 
other forms. Thus Boveri (1) has shown that in the Heteropods 
the centrospheres of the second polar spindle arise by division 
from the inner centrosphere of the first. A stage exactly simi- 
lar to my Fig. 6 has been figured and described by Mead (7) for 
Chetopterus indicating that a similar mode of origin of the 
second polar spindle occurs in that annelid. More recently 
Korschelt (6) has described the maturation in the egg of another 
annelid Ophryotrocha, from which it appears that, in mode of 
derivation of the second polar centrosome, Ophryotrocha agrees 
with Thalassema, save that in the former the centrosome is re- 
presented by a body of considerable size. 
It is interesting to note that in several cases the second polar 
telophase shows the centrosome again divided and with the 
halves more or less diverged, as though preparing for a third 
