1895.] Embryology. 63 
hours. These sperms have a long head with a spine at its lip, a mid- 
dle piece of some length and a long tail. They are found free in the 
cocoons for some ten minutes after laying and then penetrate the eggs. 
Several sperms may penetrate a single egg and all act alike in giving 
rise to peculiar conical areas of disturbance. These are more readily 
understood from the very interesting diagrammatic figures than from 
any verbal description. These figures seem to show much that the 
author does not emphasize regarding the minute protoplasmic phe- 
nomena concerned. 
The egg gives off two polar bodies after the cocoon is deposited. 
The first divides into two ; the three thus formed subsequently break up 
into spherical bodies that lie irregularly between the egg and its mem- 
brane, as many as ten being found by the time the pronuclei are 
formed. The number of chromosomes is eleven, in the first matura- 
tion spindle, in the first polar body, in the second maturation spindle, 
in the second polar body, and in the egg after this has been constricted 
off. 
The pronuclei are usually only two and do not present discovered 
differences. 
It is claimed that the nuclei are seen distributed through the cyto- 
plasm of the egg during the formation of the first maturation spindle. 
The remarkable structures known as “ polar rings” in the eggs of 
Clepsine are recognized again in this earthworm as peculiar and dis- 
similar appearances seen at opposite poles when the pronuclei are 
formed. 
Cleavage in Batrachia—A study of the phenomena that actu- 
ally take place in the cleavage of Amblystoma, Diemyctylus, Rana 
palustris, and Bufo variabilis has led Messrs. Jordan and Eycleshymer* 
to views that militate against much of the definiteness regarding the 
cleavage process that still remains in the text books. 
They find that “each egg, as a rule, possesses an individual rhythm 
of celi-division and the time intervals between the different sets of 
furrows are substantially the same in the same egg. There is, how- 
ever, considerable variation between these rhythms in different eggs.” 
Great variations occur in the way and in the relative time that cells 
divide, that cleavage planes appear, in fact, they state—“ we have 
found irregularity to be the rule, regularity the exception.” 
No importance can be attached to any agreement between the first 
plane of cleavage and the median plane of the resulting embryo, since, 
‘Idem. 
