NiO: 1, VARIATIONS IN LIMULUS POLYPHEMUS. 
83 
right half of a granddaughter. The line of concrescence of 
the heart lines will have at H/7.? on one side the right half of 
one daughter, and on the other the left half of another daugh- 
ter. These two halves cannot be said to belong to the 
same daughter without assuming some preformation jugglery 
by which the molecules of one half were shifted to the 
wrong side of the other. At //73 there is on one side of 
the concrescence line the margin of the right mesodermic 



m 
So) = PES 
all 
fee 
FIG. 10. 
Diagram of a triple embryo, to show the relation of the old and new parts. 
1+1'3 second generation, 2+ 2'; third generation, 3 + 3’. 
Original halves, 
area of a granddaughter, and on the other the margin of an- 
other granddaughter. At //7.7 the concrescence line has, on 
either side, in their original relations, the right and left mar- 
gins of the mesodermic area of the mother. We may there- 
fore call the hearts, or other organs developed along these three 
lines, respectively the mother, daughter, and granddaughter 
hearts, etc. 
In explaining the condition of the triple embryos in Figs. 
102 to 104, we shall assume that the original embryo divided 
