The Theory of Evolution res 
at one end,—the gastrea. He dignified the recapitulation 
theory with an appellation of his own, “The Biogenetic 
Law.” Haeckel’s fanciful and extreme application of the 
older recapitulation theory has probably done more to bring 
the theory into disrepute amongst embryologists than the 
criticisms of the opponents of the theory. 
In one of the recognized masterpieces of embryological 
literature, His’s “ Unsere Korperform,” we find the strongest 
protest that has yet been made against the Haeckelian 
pretension that the phylogenetic history is the “cause”’ of 
the ontogenetic series. His writes: “In the entire series of 
forms which a developing organism runs through, each form 
is the necessary antecedent step of the following. If the 
embryo is to reach the complicated end-forms, it must pass, 
step by step, through the simpler ones. Each step of the 
series is the physiological consequence of the preceding 
stage and the necessary condition for the following. Jumps, 
or short cuts, of the developmental process, are unknown in 
the physiological process of development. If embryonic 
forms are the inevitable precedents of the mature forms, 
because the more complicated forms must pass through the 
simpler ones, we can understand the fact that paleonto- 
logical forms are so often like the embryonic forms of to-day. 
The paleontological forms are embryonal, because they have 
remained at the lower stage of development, and the present 
embryos must pass also through lower stages in order to 
reach the higher. But it is by no means necessary for the 
later, higher forms to pass through embryonal forms because 
their ancestors have once existed in this condition. To take 
a special case, suppose in the course of generations a species 
has increased its length of life gradually from one, two, three 
years to eighty years. The last animal would have had 
ancestors that lived for one year, two years, three years, etc., 
up to eighty years. But who would claim that because the 
final eighty-year species must pass necessarily through one, 
