294 Agassiz— Paleontological and Embryological Development. 
Art. XX XII.— Paleontological and Embryological Development ; 
Address by ALEXANDER AGASSIZ, Vice-president of Section 
B, at the recent Boston meeting of the American Asso- 
ciation for the Advancement of Science. 
SINCE the publication of the ‘‘ Poissons Fossiles” by Agas- 
siz, and of the ‘ Embryologie des Salmonidées”” by Vogt, the 
similarity, traced by the former between certain stages in the 
growth of young fishes and the fossil representatives of extinct 
members of the group, has also been observed in nearly every 
class of the animal kingdom, and the fact has become a most 
convenient axiom in the study of paleontological and embryo- 
logical development. This parallelism, which has been on the 
one side a strong argument in favor of design in the plan of 
creation, is now, with slight emendations, doing:the duty on 
the other as a newly discovered article of faith in the new 
biology. 
But while in a general way we accept the truth of the propo- 
sition that there is a remarkable parallelism between the em- 
bryonic development of a group and its paleontological history, 
yet no one has attempted to demonstrate this, or rather to show 
ow far the parallelism extends. We have, up to the present 
time, been satisfied with tracing the general coincidence, or 
with striking individual cases. 
The resemblance between the pupa stage of some Insects and 
of adult Crustacea, the earlier existence of the latter, and the 
subsequent appearance of the former in paleontological his- 
tory, furnished one of the first and most natural illustrations of 
this parallelism; while theoretically the necessary develop- 
ment of the higher tracheate insects from their early branchiate 
aquatic ancestors seemed to form an additional link in the 
chain, and point to the Worms, the representatives of the larval 
condition of Insects, as a still earlier embryonic stage of the 
Articulates. 
beginning of the century seemed to be the most naturally cir- 
cumscribed of all. Embryology and paleontology combined 
have led to the recognition of a natural classification uniting 
Birds and Reptiles on the one side and Batrachians and Fishes 
