. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. nt (Fig. 206). In any colony a division of labor may occur among theconstituent individuals, or zooids. Thus in the simplestcases we have crawling zooids,or stolons, and feeding Hydractinia1 we have, in addi-tion, reproductive zooids, nettlingzooids, and passive, thorn-likezooids. Here we see how com-pletely subservient the individualis to the good of the subserviency has ruled in allsuccessful colonies of animals. Regeneration. — Closely allied tothe power of budding is that
. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. nt (Fig. 206). In any colony a division of labor may occur among theconstituent individuals, or zooids. Thus in the simplestcases we have crawling zooids,or stolons, and feeding Hydractinia1 we have, in addi-tion, reproductive zooids, nettlingzooids, and passive, thorn-likezooids. Here we see how com-pletely subservient the individualis to the good of the subserviency has ruled in allsuccessful colonies of animals. Regeneration. — Closely allied tothe power of budding is that ofreproducing a lost organ. Suppos-ing the head (mouth and ten-tacles) of a Hydra to be cut off, the base will reproduce the lost head. Suppose the base to beremoved, the head will reproduce a new base. When aHydra is cut in two transversely, two Hydras result whereformerly there was only one. Even three or more Hydrasmay arise when a Hydra has been cut into so many other conditions are favorable to life, you canhardly kill a Hydra by mutilation. A trace of this i Fig. FIG. 206. — Idylia, a sea-walnut, seen from thebroad side. Half nat. size.«, anal opening ; b, lateraltube; c, circulai-tube; d,<,f, g, ft, rows of Agassi/. 220 ZOOLOGY capacity for regeneration, as it is called, is seen also inman when a wound heals, and a diseased organ, even whenpartly destroyed, is made whole again. APPENDIX TO CHAPTER XIV KEY TO THE PRINCIPAL SUBDIVISIONS OF THE CNIDAKIA a\. Body composed of 4, 6, or many rays ; nettling organs well \. Mouth at apex of an oval cone; cavity simple Class c\. Existing for the most part in 2 forms ;a sessile one, hydroid; and a free-swimming one, medusa. The hydroidform is sessile ; the medusae aremostly small, or may remain at-tached to the hydroid . Orderc2. Free-swimming colonies composed ofhydroid and medusoid individualsbudded on a floating stem . Order 62- Mouth at bottom of an oral crater ; cavity di-vi
Size: 1278px × 1955px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1900
