1851.] OF THE ROYAL INSTITUTION. 15 
It generally happens that the metamorphosis which has been 
described as occurring after the seventh or eleventh generation takes 
place much earlier in the case of some of the thousands of indi- 
viduals so propagated: just as a leaf-bud near the root may develope 
a leaf-stem and a flower with much fewer antecedent generations of 
leaves from buds than have preceded the formation of the flower at 
the suminit of the plant; or just as one of the lower and earlier formed 
digestive polypes may push out a bud to be transformed into a pro- 
creative and locomotive polype. The same analogy is closely main- 
tained throughout: 
The wingless larval Aphides are not very locomotive; they might 
have been attached to one another by continuity of integument, and 
each have been fixed to suck the juices from the part of the plant 
where it was brought forth. The stem of the rose might have been 
incrusted with a chain of such connected larve as we see the stem 
of a fucus incrusted with a chain of connected polypes, and only the 
last developed winged males and oviparous females might have been 
set free. The connecting medium might even have permitted a 
common current of nutriment contributed to by each individual to 
circulate through the whole compound body. But how little of 
anything essential to the animal would be affected by cutting through 
this hypothetical connecting and vascular integument and setting 
each individual free! If we perfurm this operation on the compound 
zoophyte, the detached polype may live and continue its gemmiparous 
reproduction. This is more certainly and constantly the result in 
detaching one of the monadiform individuals which assists in com- 
posing the seeming individual whole called ‘ Volvox globator ;’ and 
so likewise with the leaf-bud. And this liberation Nature has actually 
performed for us in the case of the Aphis, and she thereby plainly 
teaches us the true value or signification in morphology of the con- 
necting links that remain to attach together the different gemmi- 
parous individuals of the volvox, the zoophyte, and the plant. 
The analogy between the procreating larve of the Aphis, the 
Medusa, and the Coralline is so true and so close, that if the larval 
Aphis be a distinct individual and not a part, so must be the strobila, 
the planula, and the gemmiparous leaf: if the succession of larval 
Aphides be truly described, as a succession of generations, so must 
that succession of planula, polype, and strobila which leads to the 
oviparous Medusa; and that succession of planule and nutritive 
polypes which precede the detachment of the free procreative 
medusiod polypes in the Coryne; and the like with the plant-gene- 
rations preceding the flower. 
It would have been easy, if time permitted, to multiply the illus- 
trations of the essential condition of these phenomena. That 
condition is, the retention of certain of the progeny of the primary 
fertilized germ-cell, or in other words, of the germ-mass, unchanged 
