. Fishes. Fishes. The Leptocardii, or Lancelets i6 5 their actual common ancestry with the fishes, they must ap- proach near to these in many ways. Their simpHcity is largely primitive, not, as in the Tunicates, the result of subsequent degradation. The lancelets, less than a dozen species in all, constitute a single family, BranchiostomidcB. The principal genus, Branchi- ostoma, is usually called Amphioxus by anatomists. But while. Fig. 115.—California Lancelet, Branchiostoma caU]orniense Gill. (From San Diego.) the name Amphioxus, like lancelet, is convenient in vernacular use, it has no sta
. Fishes. Fishes. The Leptocardii, or Lancelets i6 5 their actual common ancestry with the fishes, they must ap- proach near to these in many ways. Their simpHcity is largely primitive, not, as in the Tunicates, the result of subsequent degradation. The lancelets, less than a dozen species in all, constitute a single family, BranchiostomidcB. The principal genus, Branchi- ostoma, is usually called Amphioxus by anatomists. But while. Fig. 115.—California Lancelet, Branchiostoma caU]orniense Gill. (From San Diego.) the name Amphioxus, like lancelet, is convenient in vernacular use, it has no standing in systematic nomenclature. The name Branchiostoma was given to lancelets from Naples in 1834, by Costa, while that of Amphioxus, given to specimens from Corn- wall, dates from Yarrell's work on the British fishes in 1836. The name Amphioxus may be pleasanter or shorter or more familiar or more correctly descriptive than Branchiostoma, but if so the fact cannot be considered in science as affecting the duty of priority. The name Acraniata (without skull) is often used for the lower Chordates taken collectively, and it is sometimes applied to the lancelets alone. It refers to those chordate forms which have no skull nor brain, as distinguished from the Cramota, or forms with a distinct brain having a bony or cartilaginous capsule for its protection. Origin of Lancelets.—It is doubtless true, as Dr. Willey sug- gests, that the Vertebrates became separated from their worm- like ancestry through "the concentration of the central nervous system along the dorsal side of the body and its conversion. 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 Jordan, David Starr, 1851-1931. New York, H. Holt and Company
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