The principles of biology . of theAmoeba-]ikG individuals composing it. § 202. A truth which we before saw among plants, wehere see repeated among animals—the truth that as soon asthe integration of aggregates of the first order into aggregatesof the second order, produces compound wholes so specific intheir shapes and sizes, and so mutually dependent in theirparts, as to have distinct individualities; there simultaneouslyarises the tendency in them to produce, by gemmation, othersuch aggregates of the second order. The approach towardsdefinite limitation in an organism, is, by implication, an
The principles of biology . of theAmoeba-]ikG individuals composing it. § 202. A truth which we before saw among plants, wehere see repeated among animals—the truth that as soon asthe integration of aggregates of the first order into aggregatesof the second order, produces compound wholes so specific intheir shapes and sizes, and so mutually dependent in theirparts, as to have distinct individualities; there simultaneouslyarises the tendency in them to produce, by gemmation, othersuch aggregates of the second order. The approach towardsdefinite limitation in an organism, is, by implication, an ap-proach towards a state in which growth passing a certain point,results, not in the increase of the old individual, but in theformatiorij of a new indi-vidual. Thus it happensthat the common polypebuds out other polj^es,some of which very shortlydo the like, as shown inFig. 148: a process paral-leled by the fronds of sundry Algce, and by those of the lowerJungermanniacece. And just as, among these last plants, the 6 *. 84 MORPHOLOGICAL DEVELOPMENT. proliferously-produced fronds, after growing to certain sizesand developing rootlets, detach themselTes from tteir parent-fronds; so among these animals, separation of the youngones from the bodies of their parents, ensues when they hareacquired tolerably complete organizations. There is reason to think that the parallel holds stiQ fur-ther. Within the limits of the Jungermanniacece, we foundthat while some genera exhibit this discontinuous develop-ment, other genera exhibit a development that is similar toit in all essential respects, save that it is continuous. Andhere within the limits of the Hydrozoa, we find, along withthis genus in which the gemmiparous individuals are pre-sently cast off, other genera in which they are not cast off, butform a permanent aggregate of the third order. Figs. 149and 150, exemplify these compound Hydrozoa—one of themshowing this mode of growth so carried out as to produce asingle axis; and t
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectbiology, bookyear1864
