90 PROF. W. GARSTANG ON THE THEORY OF RECAPITULATION : 
iind Actheres (1914, pp. 22, 206), the young resemble the young stages far 
more closely than they resemble the adult stages of their respective "normal" 
relatives *. The symmetrical larva of Pleuronectids is scarcely distinguishable 
from many Teleostean larvse of other families : it is distinct from any existing 
or fossil adult Teleost. It is the adult Oyster which has lost its foot, not the 
young Oyster which has acquired it. It is the adult Portunion which has 
lost its legs, not the young Portunion which has acquired them by tachy- (or 
any other kind of) genesis from its adult ancestors ! These cases are all in 
the same category as the case of the wingless Moths already discussed. No 
new stage has been added to the life-cycle. One adult stage has been trans- 
formed into another, but the penultimate stages remain as before. The 
protagonist has missed his point, and the riposte is obvious. It was not his 
task to prove that Oysters were Mollusks, that Hermit-Crabs were Crustacea, 
or Pleuronectids Fishes. Comparative Anatomy did that long before the 
science of Embryology staked its claim. His province was to show that by 
virtue of Haeckel's Biogenetic Law he could reconstruct the prominent 
features of an adult ancestor from a developmental stage. All he has done 
is imperfectly to confirm Von Baer's pras-Haeckelian doctrine, that animals 
resemble one another more closely in their young stages than in their adult 
stages t- For his own illustrations show how greatly the adult may differ 
from the larva. He has merely shown the resemblance between the larvse 
of a given class. It follows that, for all he has shown to the contrary, the 
" tjrpical " or '' normal " larvse, which the Pleuronectid larva resembles, 
might have grown into Cod, Mackerel, or any other type of Teleost, and 
that the adult ancestors of Pleuronectids, so far from being " normal," may 
have carried themselves upside down like a Remora, or stood on their tails 
like Pipefishes. If no more relevant evidence than this is forthcoming, 
I claim that the old Biogenetic Law of adult recapitulation is dead, and that 
Morphology is henceforth free from a delusive and cramping hypothesis. 
Ontogeny is not a lengthening trail of dwarfed and outworn gerontic stages. 
Youth is perennially youth and not precocious age. 
12. It is true that ontogeny could not exhibit its normal progressive 
diflTerentiation of structure if evolution had always been of the type exhibited 
by these examples of metamorphic Insects, Lamellibranch Mollusks, parasitic 
Crustacea, and Pleuronectid Fishes. Evolution within these groups to-day 
partakes mostly of the nature of an adaptive radiation of the various types, 
whereas the general lines of ontogeny correspond rather with that kind o£ 
evolution which involves morphological and physiological progress. 
Although a detailed examination of any of these various advances falls 
* Note especially the absence of the 8th pair of thoracic limbs iu Epicarid, as in all 
other Isopod larvae. 
t " Im Grunde ist also nie der Embryo eicer hoheren Tierform eiuer anderen Tierform 
gleich, sondern nur ihrem Embryo" (1828, p. 220). 
