No. 1I.] REGENERATIVE ENERGY. 33 
of Clepsine ; and the same, or a closely analogous constriction, 
has been described by Kupffer and Benecke! (p. 19) in the egg 
of Petromyzon, and by Ransom !* (pp. 463, 464, 477, 479) in the 
egg of the Stickleback and some other fresh-water teleosts. 
This constriction has been confounded by the last mentioned 
authors with yolk-contraction, and brought into connection with 
the formation of the perivitelline space (‘ breathing-chamber ’ of 
Ransom, ‘ Eiraum’ of Kupffer and Benecke). This space prob- 
ably results from contraction of the vitellus as well as from 
expansion of the egg membrane, but the constriction is a 
special act of the vitellus to expel the polar globule. The elim- 
ination of polar globules is thus a process involving co-op- 
erant actions of both factors; and if the part performed by 
the polar amphiaster is karyokinetic, the associated act of the 
vitellus may be characterized as cytokinetic. I have before 
referred to the centrifugal movement of the germinal vesicle 
as an instance of repellant action, and I regard this constriction 
as a part of the same action. Jf zs thus a phenomenon of 
maturation, not of impregnation. 
Ransom, as well as Kupffer and Benecke, explains the phe- 
nomenon as a result of the penetration of the spermatozoon, 
and hence has failed to distinguish it from other phenomena of 
a similar, though not identical, nature. Bearing this fact in 
mind, we are enabled to find in their descriptions — especially 
that of Ransom — an exact parallel of the special constriction 
which always accompanies the formation of polar globules in 
Clepsine. Ransom’s account is extremely interesting, and has 
attracted so little: attention from later embryologists, that it 
seems worth while to introduce a portion of it here. After 
stating that slow contractions begin from the first moment of 
entry of the spermatozoa, causing first a flattening of the ger- 
minal pole, and afterwards slight changes of outline due to 
‘travelling waves’ at other parts of the surface, he proceeds as 
follows : — 
“Gradually more vivid contractions commence, at various 
times after fecundation, according to the temperature. In warm 
weather they have been noted in six minutes, in cooler weather 
18 Der Vorgang der Befruchtung am Eie der Neunaugen. Kénigsberg, 1878. 
14 Observations on the Ovum of Osseous Fishes. Proc. Roy. Soc. London, 
VII., 1856. 
