PHENOMENA OF ORGANIC NATURE 327 
nd inquire whether we cannot go back yet 
| her and bring down the whole to modifications 
of one primordial unit. The anatomist cannot do 
is ; but if he call to his aid the study of develop- 
ent, he can doit. For we shall find that, dis- 
inct as those plans are, whether it be a porpoise 
or man, or lobster, or any of those other kinds I 
lave mentioned, every one begins its existence 
with one and the same primitive form,—that of 
the egg, consisting, as we have seen, of a nitro- 
genous substance, having a small particle or nucleus 
in the centre of it. Furthermore, the earlier 
changes of each are substantially the same. And 
‘itis in this that lies that true “unity of organi- 
“sation” of the animal kingdom which has been 
guessed at and fancied for many years ; but which 
it has been left to the present time to be demon- 
“strated by the careful study of development. But 
is it possible to go another step further still, and 
te show that in the same way the whole of the 
“organic world is reducible to one primitive con- 
dition of form? Is there among the plants the 
Same primitive form of organisation, and is that 
‘identical with that of the animal kingdom? The 
Te ply to that question, too, is not uncertain or 
doubtful. It is now proved that every plant 
begins its existence under the same form ; that is 
