A CRITICAL RE-STATEMENT OF THE BIOGENETIC LAW. ©9 
of recapitulation from the embr3'ological side. I have already shown that, 
ill its original and general sense, recapitulation is a fact which was recognised 
long before there were any theories to account for it. But this generalised, 
or Meclielian, recapitulation needs to be clearly distinguished from the 
specifically adult recapitulation of Haeckel and his school, who could not 
understand the origin of the former except on a theory of catenary ancestral 
inheritance, each term in the ontogeny (except the last) being moulded after 
tlie likeness of a specific adult ancestor — though, of course, condensed, 
abbreviated, telescoped, and secondarily modified by adaptive changes. Now, 
the only way that I can see of establishing this theory by purely embryo- 
logical methods, is to show that the penultimate stage of the ontogeny of 
a given type of adult resembles the final (adult) stage of the ontogeny of 
some theoretically ancestral type more closely than it resembles the corre- 
sponding penultimate stage of the same, and similarly with regard to the 
antepenultimate stage, and so on. I cannot find that this has been done, or 
even attempted, in any case — certainly not in any of the cases recently 
selected by MacBride for discussion. Yet this is his thesis: •'When we 
assert that a Metazoan recapitulates in its life-history the past history of the 
race or stock to which it belongs, we mean that the stages intervening 
between the egg and the adult form resemble in some of their prominent 
features the adult animals which belonged to the same stock at different 
epochs in the past history of the race" (1917, p. 425) ; and he is concerned 
to show both that the adult stage of the ontogeny of a new species is an 
addition to the ancestral ontogeny (1914, pp. 23, 650), and that the adult 
stage of the ancestral ontogeny is reproduced (" recapitulated ") in the 
ontogeny of the new species as the last larval (or "neanic") stage (I.e. 
pp. 21, 22). But his method of establishing these points is merely to select 
a number of cases in which the adult deviates considerably from the normal, 
and to show that " the young form resembles the type of the order to which 
the parent belongs and not the parental type itself" (1917, p. 428). 
" Thus the young Hermit-Orab swims freely about in the water and has a 
symmetrical abdomen like that of Shrimps and Prawns'' [but so have the 
young stages oE these creatures!] ; "the young Flatfish swims with its 
ventral edge down and its dorsal edge up, and has an eye on each side of th& 
head" [but so have the young of all Teleostei!] ; "the young Comatulid 
is fixed to the bottom by a stalk like other Crinoids [and their young too, in 
all probability !] ; and the young American Oyster possesses a foot like that 
of other bivalves by which it crawls about" [and, I may add, as the young 
of nearly all other Lamellibranchs crawl about ! ]. Nowhere does he show, 
or claim to show, that the young stages of any of these animals resemble 
the adult more closely than the young stage of typical members of their 
respective orders. He does not show it because he cannot. In every case 
that he discusses, whether the above, or the cases of the parasitic Portunion 
