466 MEAD. [Vou. IX. 
The eggs of Amphitrite ornata are much larger than those 
of Lepidonotus, and from the first there is a segregation 
of yolk at the lower pole. The direction of every cell-division 
up to the sixty-four-cell stage is the same as in Lepidonotus. 
There is also almost as great regularity in the time of the 
divisions. 
There is not, however, the same regularity in the size of the 
cells. The first division is unequal, and the divisions up to eight 
cells are very similar to those of Nereis. The descendants of 
the large macromere LY of the eight-cell stage (I shall use 
Wilson’s nomenclature in this paper) are different, both in 
absolute and relative size, from the corresponding cells of the 
other quadrants, and exhibit an increasing tendency to more 
frequent division. 
At the sixty-four-cell stage the regularity in the cleavage 
stops. Sixteen of the cells (prototrochal) at once acquire cilia 
and never divide again. The four cells which form the cross 
do so by dividing bilaterally, as in Lepidonotus. Other cells 
divide in a plane which is oblique to the meridian, but in the 
same direction as the previous division, while still others continue 
alternating in direction of cleavage, as in the earlier stages. 
The eggs of the Maldanid Clymenella torquata have two or 
three times the diameter of the Lepidonotus eggs, have a large 
amount of opaque yellow yolk, and develop into a compara- 
tively sluggish trochophore. The cleavage is extremely regular 
up to the sixty-four-cell stage, the direction of each cleavage 
being the same as in Lepidonotvs and Amphitrite. In the 
relative size of the cells, and in the time-rythm, it is very 
similar to Amphitrite. The cross and rosette are formed in 
exactly the same manner. Again, as in Amphitrite, immedi- 
ately after the sixty-four-cell stage certain cells divide obliquely 
to the meridian, but in the same direction as the previous 
cleavage. 
While in Lepidonotus the cells of the eight-cell stage are 
all of nearly equal size and clearness, in Scolecolepis viridis 
the four apical cells are relatively very small and perfectly 
transparent ; the four vegetative cells, on the other hand, are 
huge in proportion, and opaque. 
