Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . f the utmostimportance for understanding thereal affinities of animals very dif-ferent in appearance, as is readilyshown by the following butterfly and the earth-wormseem, at the first glance, to haveno relation whatever. They differin their organization no less than intheir outward appearance. But oncomparing the caterpillar and theworm, these two animals are seenclosely to resemble each other. Theanalogy,however, is only t
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . f the utmostimportance for understanding thereal affinities of animals very dif-ferent in appearance, as is readilyshown by the following butterfly and the earth-wormseem, at the first glance, to haveno relation whatever. They differin their organization no less than intheir outward appearance. But oncomparing the caterpillar and theworm, these two animals are seenclosely to resemble each other. Theanalogy,however, is only transient;it lasts only during the larva state of */ the caterpillar, and is effaced as itpasses to the chrysalis and butter-fly conditions. The latter becoming a more and more perfect ani-mal, whilst the worm remains in its inferior state. & 562. Similar instances are furnished by animals belong;- J 4/ ing to all the types of the animal kingdom. Who wouldsuppose, at the first glance, that a barnacle, or an anatifa, weremore nearly allied to the crab than to the oyster ? And,nevertheless, we have seen (§ 553), in tracing back the anatifa Fig. 358 METAMOEPHOSES OF ANIMALS. to its early stages, that it then bears a near resemblance to alittle crustacean (fig. 370 d). It is only when full grownthat it assumes its peculiar mollusk-like covering. § 563. Among the cuttle-fishes there are several, theLoliffo, for example, which are characterized by the formof their tentacles, the two interior being much longer thanthe others, and of a different form; whilst, in others, as theOctopus, they are all equal. But if we compare the young,we find that in both animals the tentacles are all equal, thoughthey differ in number. The inequality in the tentacles beingthe result of a further development. § 564. Among the radiata, the Pentacrinus and the Co-matula exemplify the same point. The two are very differentwhen full grown, the latter being a free-swimming star-fish(fig. 373), while th
Size: 1564px × 1598px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
