CHAPTER II. 



PHYLUM CEPHALOCHORDA.* 



With dorsal tubular nerve-cord, and persistent notochord extend- 

 ing forwards in front of the nerve-cord. The muscular system and 

 gonads are segmented, and the pharynx possesses a large number of 

 branchial slits which open into an atrial cavity and are provided 

 with tongue bars. Without paired fins, jaws, brain, vertebrae 

 and generative ducts. The larval life is prolonged and the larva 

 is remarkably asymmetrical. 



The phylum Cephalochorda contains but the single genus, 

 Amphioxus Yarrell. It was discovered by Pallas in 1778, who 

 took it for a slug and named it Limax lanceolatus. Its true 

 position in the animal kingdom was first recognized in 1834 by 

 Costa, by whom it was named Branchiostoma. Two years later 

 it was described by Yarrell, who called it Amphioxus, by which 



* J. Miiller, Ueber den Bau und die Lebenserscheinungen des Branchi- 

 ostoma lubricum (Amphioxus lanceolatus), Berlin, 1844. Quatrefages, 

 " Sur le systeme nerveux et sur 1'histologie du Branchiostome," Ann. des 

 Sci. Nat. (3), 2, 1845. Kowalevsky, " Entwick, v. Amphioxus lanceolatus," 

 Mem. Acad. Imp Sc., St. Petersbourg (7), 2, 1867. Id. " Weitere Studien, 

 etc.," Arch. f. mic. Anat. 13, 1877. Stieda, " Ueb. d. Amphioxus lanceo- 

 latus," Mem. Acad. Imp. Sc., Petersbourg, (7), 19, 1873. Rolph, " Ueb. 

 d. Bau d. Amphioxus," Morph. Jahrb. 2, 1876. Langerhans, " Zur Anat. 

 d. Amphioxus," Arch. mic. Anat., 12, 1876. A. Schneider, Anat. u. Ent- 

 wick. der Wirbelthiere, Berlin, 1879. Hatschek, " Ueb. d. Entwick. Am- 

 phioxus," Arb. a. d. Zool. Inst. Wien, 4, 1881, also Zool. Anz., 7, 1884, 

 p. 517, and Anat. Anz., 3, 1888, p. 662. Rohon, " Ueb. Amphioxus lanceo- 

 latus," Denksch. k. Akad. d. Wissenschaft, Wien, 45, 1882. Lankester, 

 " Contributions to the knowledge of Amphioxus lanceolatus," Q.J.M.S., 29, 

 1889, p. 364. MacBride, " The Early Development of Amphioxus," 

 Q.J.M.S., 40, 1898, p. 589. A. Willey, Amphioxus, etc., New York, 1894, 

 and Q.J.M.S., 31, 1890, p. 445, and 32, 1891, p. 183. v. Wijhe, " Beitr. z. 

 Anat. des Kopf region des Amphioxus," Petrus Camper, 1901, and Anat. 

 Anz., 8, 1893. C. F. Cooper, " Cephalochorda," in J. S. Gardiner's Fauna 

 etc. of Maldive and Laccadive Archipelago, 1, 1903, p. 347. R. C. Punnett, 

 " Meristic Variation in Cephalochorda," Ibid., p. 361. 



