Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . 340 EEPHODUCTI01ST. Fig. Fig. 358. tion, is still more extraordinary; it takes place only in polyps and some infusoria. A cleft, or fis-sion, at some part of the body takesplace, very slight at first, but con-stantly increasing in depth, so asto become a deep furrow, like thatobserved in the yolk, at the begin-ning of embryonic development; atthe same time the contained organsare divided and become double, andthus two individuals ar
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . 340 EEPHODUCTI01ST. Fig. Fig. 358. tion, is still more extraordinary; it takes place only in polyps and some infusoria. A cleft, or fis-sion, at some part of the body takesplace, very slight at first, but con-stantly increasing in depth, so asto become a deep furrow, like thatobserved in the yolk, at the begin-ning of embryonic development; atthe same time the contained organsare divided and become double, andthus two individuals are formed ofone, so similar to each other that itis impossible to say which is theparent and which the division takes place sometimesvertically, as, for example, in Vorti-cella (fig. 357, c, d), and in some po-lyps (fig. 358, a, d) ; and sometimestransversely. In some infusoria, theParameeiafoY instance, this divisionoccurs as often as three or fourtimes in a day. § 513. In consequence of thissame faculty many animals are ableto reproduce various parts of theirbodies when accidentally lost. It is well known that crabsand spiders, on losing a limb, acquire a new one. T
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
