Antithetic Alternation of Generations. 443 
import and not directly treating of the particular form under 
examination, as though based on revelation and not to be 
impugned. Thus the facts and factors pointing to heterodox 
conclusions are liable to be ignored, and the total of new 
knowledge gleaned falls readily into line with previous 
beliefs. 
So opposed to tradition does a new view seem that, when 
the deciding fact in its favour is finally discovered, the whole 
thing is looked upon as little short of a miracle. There are 
plenty of apparently meaningless facts in the possession of 
zoological science ; but the most insignificant fact has some 
meaning, and it may often happen that the explanation of 
it is not to be directly got at. Many ways lead to Rome, 
some directly, others by circuitous paths. 
When some seven years ago I began to follow the history 
of a few insignificant ganglion-cells in Lepidosteus and other 
oviparous Ichthyopsida it never seemed in the least likely 
that the end of the chapter would be found in the processes 
which occur during oogenesis, spermatogenesis, and conjuga- 
tion. Any connection with spore- formation and an antithetic 
alternation of generations, such as that found in the Meta- 
phyta, would at that time, and long afterwards, have appeared 
to me to be utterly absurd and chimerical. The track from 
the start almost to the finish has been a complex and 
puzzling one. Often it has been dark and ill-defined, and 
the goal has kept itself concealed until well-nigh the journey’s 
end. 
When the e supposed law of Metazoan development ’ 1 was 
written, the recognition of any very close similarity in the 
laws governing animal- and plant-development seemed some- 
what remote. All along the desire has been to study the 
facts, to ignore none, and not to be biased by theoretical 
considerations. For a long time no decisive facts were un- 
earthed ; but, ultimately, putting together various facts con- 
cerning larvae and their fate, their morphology, and their 
Beard, J., On a supposed Law of Metazoan development. Anat. Anz. 1892. 
