i8 



ANATOMY OF AMPHIOXUS. 



the buccal cartilages. As pointed out by Johannes Miiller, 

 they are not to be compared with the jaw-apparatus, nor 



to the hyoid or tongue- 

 bone of the jaw-bearing 

 Vertebrates, but they 

 belong to the same cate- 

 gory as the mouth-carti- 

 lages of the Cyclostome 

 fishes (which possess a 

 hyoid cartilage in addi- 

 tion) and the labial car- 

 tilages of Selachians 

 (sharks). 



The absence of paired 



auditory organ has been 



Fig. 3. — Anterior portion of body of young 

 transparent individual. (After J. MiJLLER, 

 slightly altered.) 



ck. Notochord. ci. Buccal cirri, e. Eye- 

 spot, etid. Endostyle. />-. Fin-rays lying in 

 the fin-chambers. ' g.s. Gill-slits; the skeletal Syes and of any kmd.of 

 rods of the gill-bars are indicated by blaek lines. 

 nt. Spinal cord, with pigment granules near its 

 base. ?-.(!. Downgrowth from right aorta lying mentioned aboVC. There 

 to the right of vel. the velum; with velar ten- . 



tacles projecting back into pharynx. w.(>. Riid- ^S, no\ve\er, a median 

 erorgan; ciliated epithelial tracts on inner ^yj^j^j., consists of a 



surface 01 oral hood. ^ 



comparatively large un- 

 paired pigment spot lying at the anterior extremitj- of the 

 dorsal nerve-tube.* A row of 

 similar, but much smaller, 

 masses of pigment lie along 

 the floor of the spinal canal, 

 commencing some distance 

 behind the eye (Fig. 3). 



Immediately above and be- 

 hind the eye-spot is a small f™: ^^^""^ J; ^i^ller.) The 



-' ^ basal pieces he end to end in the mar- 



pit in the body-wall reaching gin of oral hood, and each basai piece 



sends up an axial process into the 

 from the outer surface of the corresponding buccal cirrus. 



* The eye-spot has been observed to he sometimes broken up into two 

 pigment masses. (See Ayeks, No. 105 bibliog.) 



