XIII 



PHYLUM CTTORDATA 



139 



ncL.ai 



B 



specimens of ]\ryxiiie thrown into a bufkot of watoi- are capable 

 of o-elatinisiii"' the whole with their secretion. The slinie-tjlands 

 of Myxine contain peculiar " thread-cells " containing a much- 

 coiled thread which unwinds either before or after the discharge 

 of the cell from the gland. 



Myxine approaches most nearly to the condition of an internal 

 parasite of any Vertebrate ; it is said to attach itself to living 

 Fishes and gradually to 

 bore its way into the 

 coelome, devouring the 

 flesh as it goes. 



There is no true buccal 

 funnel : the space on 

 Avhich the mouth opens 

 is edged with tentacles 

 (Fig. 806) supported by 

 cartilages ; there is a 

 single median tooth 

 above the oral aperture, 

 and two rows of smaller 

 teeth on the tongue. The 

 papillae beneath the cone- 

 like horny teeth bear a 

 still closer superficial re- 

 semblance to rudiments 

 (or vestiges) of true cal- 

 cified teeth than is the 

 case in the Lamprey; but 

 it appears that no odon- 

 toblasts and no calcified 

 substance of any kind 

 are formed in connection 

 with them. The nostril 

 {iia. ap.) is a large un- 

 paired aperture situated 

 in the dorsal margin of 

 the buccal space, and 

 is continued into a pas- 

 sage, the pituitary sac, 

 which opens into the pharynx. Myxine commonly lives nearly 

 buried in mud, and the respiratory current passes through this 

 passage to the gills. 



The only fin is a narrow caudal surrounding the end of the tail. 

 The respiratory organs present striking differences in the two 

 o-enera. In Bdellostoma there are in different species six to 

 fourteen very small external branchial apertures (br. d. 1) on each 

 side, each of which communicates by a short tube ^vith one of 



br.cl.i 



br.tzp 



oes.ct 



Fid. no;.— Head 



jf n^yxine glutinosa (A) and of 



Bdellostoma forsteri (B), fi-uw beneath. Ur. ap. 

 brancliiiil aperture ; br. cl. 1, first branchial cleft ; 

 iiith. mouth ; mi. ap. nasal aperture ; (ks. ct. d. teso- 

 phageo-cutaneous duct. The smaller openings in A 

 are tho.se of the mucus-glands. (After W. K. Parker.) 



