. A manual of zoology. Zoology. 32 GENERAL TRIXCirLES OF ZOOLOGY loLjically the most highly devek^ped fishes are first diphyccrcal, later heterocereal, and finally become homocercal. Last of all, paleonto- louncally the oldest fishes are diphycercal or heterocereal, and only later do homocercal forms Fig. io.âTail-lms of various fishes (from ZittclV --1, Tiiphvccrcal fm of Polvplents bichir. (\'crtebral column anil notocliord divide the tail into symincUical dorsal and ventral portions.) B, Heterocereal tail of the sturgeon. (As a result cf an upward bending c>f the notoehord and ^
. A manual of zoology. Zoology. 32 GENERAL TRIXCirLES OF ZOOLOGY loLjically the most highly devek^ped fishes are first diphyccrcal, later heterocereal, and finally become homocercal. Last of all, paleonto- louncally the oldest fishes are diphycercal or heterocereal, and only later do homocercal forms Fig. io.âTail-lms of various fishes (from ZittclV --1, Tiiphvccrcal fm of Polvplents bichir. (\'crtebral column anil notocliord divide the tail into symincUical dorsal and ventral portions.) B, Heterocereal tail of the sturgeon. (As a result cf an upward bending c>f the notoehord and ^â ertcl^ral column the fin has become asymmetrical, the ventral portion much larger than the dorsal.) C", D, Homocercal hns, C", of Amia calva; D, of Tnitta salar. (By a still greater upward bending of the notoehord and vertebral column the dorsal portion has almost entirely disappeared and the ventral portion almost alone forms the fm, externally apparentU' s'snumetrical, but in its internal structure ^"e^y asymmetrical.) c//, chorda; a, l\ r, co\'er-plates. \\Tiat has here been referred to is onh- a small fraction of the proofs which morphology offers in fa^â or of e\ohition; it can only serve to show how morphological observations can lie employetl. I'or the retlecting naturalist the facts of morphology are a great inducti\e proof in favor of the theory of e\ Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
