64 The Vegetuble Individual in its relation to Species. 
generation as now: known, and substantiate the pertinent words 
of Gethe with which Steenstrup opens his Memoir: ‘“ Nature 
keeps on her course, and what seems an exception is in rule.” 
It was Sars, however, who first gave the answer to the riddle, 
the key to the newly opened domain, when he said of the course 
of development of Medusa, that here “it was not the individual, 
but the generation, which underwent the metamorphosis.’”* This 
was the true point of view; for Steenstrup dwelt too exclusively 
n the physiological side, the functional relat@®ns, of the alter- 
malian generations. Steenstrup, in fact, considered that the sig- 
nificance of alternation of generation consisted in its being an 
organic nursing of the brood connected with particular genera- 
tions, for which reason he termed the individuals of these genera- 
tions “ nurses ;’—a mode of viewing the subject, which, with all 
Steenstrup’s pregnant elaboration of his idea, and with all the 
analogies he pointed out between it and the well-known phe- 
nomena of nursing the brood by particular individuals among 
Ss, Wasps, ants and termites, does not seize the essential point 
of the phenomenon of alternation of generations + R. Leuck- 
hardt{ conceives alternation of generation from a more compre- 
hensive physiological point of view, in connection with the to- 
tality of all the other phenomena of the formation of different 
individuals, whether it ocenrs in a erent or in the same geve- 
ration; regarding all these phen a from the point of view of 
a division, not merely o f the aaaie ae but of the vital task in 
ete ral, among certain individuals; considering itasa pol ymorph- 
sim determined by a division of labor. But even this view must 
lead to the morpliological one; for the division of labor is deter= 
SHG, e. 29. This assertion, of course, must not be ea sr if the : 
Garticel ar generation did not come in for its part of a metamorphosis. Sars’ view 
is most beautifully corroborate comparison to lants; as in plants the meta- 
= aaa pla 
morphosis of the re itself is connected with the formation which leads to the 
sonal a ag new parts, which in their turn have their own subordinate meta- 
mo 
Hl pvomnes ee 8 ne so is mg correct in eet to er niofoky of the devel- 
opment of Distome, whose n and grand-nurses < last utricles entirely 
led with the brood and form Kinning mere re ceptactee:o f the br ood. Its application 
is less happy to those cases where the roman from the Boke nie ry generations to 
the final gen generation ta tole a canta ernal shoot- or bud-formation, as in Ser- 
nulari 
case. tak wi 
out any alternation of generation in a great number of animals (Ascidia, Bryoz04, 
Madrepora), and by division as well (Astrea, Annulata, Iyuertas These cases are 
comparable to the occurrence o of wnessential branches in plants; while alternation 
rE RSL ac Sih oc tga ar 
e ‘0! us vy. ercmrae 
Beitrag z. 2 Lehre v . Generationsw, (185 1.) 
2% 
