94 PATTEN. [VoL. XII. 
Increased vitality is shown by increased size, persistency of 
form, and by the production of new organs in the reverse way 
of that in which they disappear. If the increase is due to the 
original presence of an increased amount of formative material 
in the ovum, the increase in size, vitality, and number of organs 
will be a permanent characteristic of the individual ; but if it is 
due to the accelerating action of the environment, there will 
be a corresponding loss at some other time or place. We may 
further conclude that : 
(1) In multiple embryos of Limulus the new organs are 
formed by forced drafts on the old material. 
(2) That the new halves are weaker in formative power than 
the old. 
(3) That equality is established by the interchange of ma- 
terial from the stronger to the weaker halves. 
(4) That at first, the sum total of formative energy in 
both halves of embryo C is less than in Z, and in B than 
in A. 
(5) That equality is finally established between all these 
embryos by interchange of material, so that in the end all 
three are reduced to the same grade of degeneration. 
(6) In defective single embryos, the absent parts are absent 
because their specific formative material was absent. Theo- 
retically the absent organs might be restored by forced growth 
of the other side. But there is no reason to expect forced 
growth will occur in an embryo already defective in formative 
material. If it does occur, it will more likely be at the an- 
terior end, and of course the restoration will not be detected. 
If it does occur in that way, it explains why unilateral defects 
are more frequently seen at the posterior than at the anterior 
end. 
VII. DEGENERATION AND DEATH OF LimuLUS EMBRYOS. 
The causes of degeneration and death of the embryos de- 
scribed in the preceding sections are due to abnormal limita- 
tions in either the power of division, specialization, or longevity 
of the cells, or to various combinations of the same. 
