No. I.] VARIATIONS IN LIMULUS POLYPHEMUS. 89 
This point, as we have already shown, is the median part of 
the most anterior end of the body. The tension there would 
be most likely to be relieved by the production of a new organ 
at that point, exactly duplicating in size and differentiation the 
one side of which it was formed. If the differentiation tension, 
if we may use the term, is still too great, it will be relieved by 
the production of more new organs at the next point of greatest 
differentiation, namely, at a point lateral to the two newly 
formed organs, and on the median side of the corresponding 
organ in the next posterior segment. The process might 
go on till two entirely new halves were produced in that 
way, or it might stop at any time that the extra tension was 
relieved. 
This supposition may in a measure account for the remark- 
able fact that the newly formed organs do not pass through 
the various stages of development the other organs did, but 
assume at once whatever characters the old organs may have 
at that time. For example, the tip of the new unpaired append- 
age in Figs. 90 and gI is just as perfect in form and character 
for that age as the other appendages on the old halves, and for 
every successive part of it that appears, it is the same. It 
looks as though the perfect appendage had been previously 
concealed in the yolk, and gradually rose to the surface point 
first, till completely exposed. 
If two entirely separate embryos are produced by this forcing 
process, the growth force, if it is an exhaustible quantity, will 
be irretrievably subdivided between two embryos. Each will 
have half the energy of the parent, provided there has been an 
equal distribution between the new and old halves. But on the 
formation of a triple embryo, the undivided one will have twice 
the energy of either of the other two. 
On the other hand, if there is at first no recuperation of 
embryo B from A, or C from &, the latter must contain the least 
amount, and C less than 4, provided there is recuperation of 
the weaker half of each embryo from the stronger during the 
process of division. This is clearly in accordance with their 
degrees of degeneration, as shown in Fig. 102. But if we 
suppose that there is subsequently a slow diffusion of formative 
