General principles of zoology . s of various fishes (From Zittel.) <-A, chorda. A, Diphycercal fin ofPolyfterus bicliir. (Vertebral column and notochord divide the tail into symmetricaldorsal and ventral portions.) B. Heterocercal tail of the Sturgeon. (As a result of anupward bending of the notochord and vertebral column the fin has become asymmetrical,the ventral portion much larger than the dorsal.) be derived. Embryologically the most highly developedfishes are first diphycercal, later heterocercal, and finally be-come homocercal. Last of all, paleontologically the oldestfishes are diph
General principles of zoology . s of various fishes (From Zittel.) <-A, chorda. A, Diphycercal fin ofPolyfterus bicliir. (Vertebral column and notochord divide the tail into symmetricaldorsal and ventral portions.) B. Heterocercal tail of the Sturgeon. (As a result of anupward bending of the notochord and vertebral column the fin has become asymmetrical,the ventral portion much larger than the dorsal.) be derived. Embryologically the most highly developedfishes are first diphycercal, later heterocercal, and finally be-come homocercal. Last of all, paleontologically the oldestfishes are diphycercal or heterocercal, and only later dohomocercal forms appear. What has here been referred to is only a small frag-ment of the weighty materials for proof which Morphologyoffers in favor of the descent theory, it can only serve toshow how morphological observations can be the reflecting naturalist the facts of Morphology are a HISTORY OF ZOOLOGY. 49 single great inductive proof in favor of the Theory cA c
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
