446 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
briefly the observations of a number of other investigators in regard 
to these phenomena and the cytoplasmic activities which have been 
seen to take place in the eggs of a number of animals widely separated 
morphologically. No definite conclusions are reached as to the 
functions of these various phenomena, but it is generally thought that 
they are concerned with fundamental intrinsic changes within the 
cytoplasm. 
These protoplasmic connections are usually composed of the ectosarc 
only. They are present not only in the two-celled stage, but in several 
of the following stages as well. As the number of cells increases, the 
connecting films become less easily recognized. 
The second cleavage occurs about twenty-five or thirty minutes 
after the first.- The plane of division is also meridional and at right 
angles to the first segmentation. It begins at, the center of the egg 
next to the furrow of the first cleavage and slowly extends out toward 
the periphery. When the division is completed the four blastomeres 
undergo a slight rotation from right to left; and in the center of the 
egg between the cells there is at times to be seen a small open space or 
segmentation cavity which may extend through the entire egg as shown 
in figure 21, plate 32. 
After a lapse of time equal to that which occurs between the first 
and second divisions, the third cleavage furrow appears. This plane 
of division is equatorial and divides the egg into eight blastomeres. 
When the segmentation is first completed the two quartets of cells are 
situated one upon the other and form a more or less spherical whole, 
as is the usual arrangement in eggs in which segmentation is equal 
and regular. This arrangement of the blastomeres is, however, of 
very short duration, for soon a separation takes place between the cells 
of the lower quartet and two of them roll away from the plane of 
separation in one direction; the other two move out in the opposite 
direction. In this migration the blastomeres move through an angle 
of 45 degrees or more, and finally come to lie in such a position as to 
form a semicircular plate as shown in figures 22 and 23 of plate 32. 
The separation and rotation of the cells of one quartet seem to be 
constant in their occurrence; but the final arrangement of the blasto¬ 
meres is not alwavs as regular and definite as that shown in the figure. 
At times they are more loosely and irregularly connected, and may 
assume relative positions similar to that shown by Metschnikoff for 
Oceania armata in figure 34, plate 1, of his “Embryologische studien.” 
