130 
J. T. CUNNINGHAM. 
Critical Remarks on Van Beneden’s and other 
Researches . 
In spite of the conclusion arrived at by O. Hertwig and Fol, 
that the polar globules were formed by a process equivalent to 
cell-division, we find on examining their works that in some 
animals certain stages of the process as described by them do 
not agree with the corresponding stages of karyokinesis. In 
karyokinesis it has been clearly shown that the whole nucleus 
is transformed into the achromatic spindle and its chromatic 
loops. If we study plate ii of Fol’s elaborate memoir 1 we 
find that in Aster ias glacial is only a portion of the ger- 
minal vesicle or spot is employed in the formation of the 
“ Amphiaster de rebut ; ” the figure is represented as originating 
entirely on the outside of the germinal vesicle. It is evident 
from that plate that a large portion of the germinal vesicle and 
spot is left to disappear in the vitellus. On the other hand, 
if we examine plate viii of the same work we find that in 
Pterotrachea the germinal vesicle and spot are entirely trans- 
formed into the spindle of the amphiaster and its equatorial 
plate. The results of Fol on other animals are not very 
decisive on this point (see figs. 15, 16, PI. X). 
If we turn now to O. Hertwig we find that his account of 
the phenomena in Hirudinea 2 supports the direct transfor- 
mation view. On the other hand, his account of the same 
phenomena in Asteracanthion (pis. vi and viii of his paper in 
‘ Morph. Jahrb./ Bd. iv) agree with the results of Fol on 
Asterias glacialis with the following difference: — He found 
that a certain portion of the germinal spot passed into the 
centre of a star, which was forming in a portion of vitelline 
protoplasm projecting into the interior of the germinal 
vesicle (see figs. 14, 18, PI. X). It is possible also 
that part of the substance of the germinal vesicle goes 
to form the spindle, but Hertwig is not very decisive on 
this point. It seems, then, that in Echinoderms the germinal 
vesicle and spot are not directly but only partially transformed 
’ * Commencement de l’henogenie,’ Geneva, 1879. 
‘Morph. Jahrb.,’ Bd. iii. 
