Paleontology and the Biogenetic Laiv. — von Zittel. 145 
The ontogeny of organisms now living would, for the rest, 
afford but an exceedingly unsafe basis for the reconstruction 
of ancient faunas and floras, since experience teaches that 
the biogenetic law is frequently veiled or completely obscured 
owing to various causes. Not seldom does it happen that of 
two nearly allied living forms the one passes through a series 
of continuous, successive stages, while development in the 
other takes place more by jumps. In the latter case the em- 
bryo is driven by peculiar influences to an acceleration of its 
development; it completely jumps over certain stages and 
thus renders unintelligible the historical (palingenetic) record 
preserved in the ontogeny of each individual. This falsifica- 
tion of development — or coenogenesis, as Haeckel calls it — 
chiefly occurs when the adult individual manifests a high de- 
gree of differentiation and when the embryo has to pass 
through considerable changes to reach its final form. How 
unsafe and deceptive palaeontological results would be if at- 
tained by embryological paths may be gathered from some 
random instances. What wonderful ancestors would be con- 
structed for the crinoids by a zoologist who only knew the 
life-history of Antedon\ The lowest portion of the family 
tree would have to present armless crowns, composed only of 
five basal and five oral plates, set on a stalk ; then would 
follow genera with five large basals, five tiny radials and five 
stout massive orals; then forms with five arms, at first short 
and later on simpljj^ branched; and so on. But I will not 
further elaborate the picture. All know that it does not in the 
remotest manner agree with the facts of palaeontology. What 
zoologist would conclude from the developmental history of 
the recent sea-urchins that the regular forms preceded the ir- 
regular, or again that the former had fossil ancestors of the 
type of the Perischoechinidai and BothriocidaridaiV In the 
ontogeny of the cojlenterates there is no certain indication of 
the former existence of Cyathophj^llidte or Cystiphyllida^ No 
observations of embryology would warrant our imagining the 
former existence of graptolites or stromatopores. No stage 
in the development of an}' living brachiopod informs us that 
numerous spire-bearing genera lived in Paheozoic and Meso- 
zoic times. These few instances might easily be multiplied; 
but they maj^ suffice to show how trivial are the discoveries 
