. The study of animal life. Zoology. 70 The Study of Animal Life PART I result from the fact that in such a large colony perfect uniformity of nutritive and other conditions is impossible. Individuals which are fundamentally and originally like one another grow to be different, and perform different func- tions according to the caste to which they belong. Many are nutritive in form like the little freshwater Hydra—tubular animals with an extensile body and with a terminal mouth wreathed round by mobile tentacles. On these the whole nutrition of the colony depends. Beside these there are reprod
. The study of animal life. Zoology. 70 The Study of Animal Life PART I result from the fact that in such a large colony perfect uniformity of nutritive and other conditions is impossible. Individuals which are fundamentally and originally like one another grow to be different, and perform different func- tions according to the caste to which they belong. Many are nutritive in form like the little freshwater Hydra—tubular animals with an extensile body and with a terminal mouth wreathed round by mobile tentacles. On these the whole nutrition of the colony depends. Beside these there are reproductive " per- sons," which cannot feed, being mouthless, but secure the continuance of the species and give rise to embryos which start new colonies. Then there are long, lank, sensitive mem- bers, also mouthless, which serve as the sense-organs of the colony, and are of use in de- tecting food or danger. When danger threatens, the polypes cower down, and there are left projecting small hard spines, which some regard as a fourth Fig. 14. —Colony of Hydractmia class of individuals—Starved, e^maiia. a, nutritive individuals; abortive members like the 0, reproductive individuals; c, abortive spines; and there are thoms on the hawthom hedge, also long mouthless individuals t rprno-nitiincr thpir iitilltv \n specialised in sensitiveness. (From in recognising tneir Utmty tO Ghamhers's Encyclop.; after All- the Colony as a whole we can "^"^^ hardly overlook the fact that their life as individuals is practically nil. They well illus- trate the dark side of division of Herbert Spencer and Ernst Haeckel have explained very clearly one law of progress among those animals which form colonies. The crude form of a colony is an aggregate of similar individuals, the perfected colony is an integrate in which by division of labour greater harmony of life has resulted, and in which the whole colony is more thoroughly compacted into a unity. Among the Stinging-.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1892
