296 Scientific Intelligence. 
limits some of the most extraordinary phenomena of generation, of growth 
and of life 
The first chapter treats briefly of the history of our knowledge in this 
branch, from the time of Aristotle, (who confounded sea-anemones and 
jelly-fishes under the common term nettles), down, through many barren 
centuries, to near our own day, when Rondelet, three hundred years ago, 
published figures of medusze, with some observations of his own. Two 
F. Miller, however, had published the Zodlogia Danica, the colored plates 
; i ; i 
logy of the 
covered-eyed meduse. Th 
polyps and the naked-eyed meduse, was shown. In 1843, De 
jardin supplied the wanting link, by discovering that the meee : 
e 
parent, though with shorter rows of flappers ; 
insects, have no proper larval condition, but gain another pair of legs on 
ty. nee 
It would be natural to challenge the standing of a class, oacaer’ = 
such seemingly heterogeneous groups. What have they in common’ 
Not a common embryology :—not a common detail of structure :—least 
of alla common form. Here then we are compelled to resort, to ¥ 
we should daily resort to, without compulsion, the metaphysics é 
it we agree to call that a class which shows a plan of structure ¢ 
out in a peculiar way; then two questions come up: Ist, what 18 
peculiar way in which the general plan of radiation is carried out 
