The Cyclostomes, or Lampreys 489 



ate; r per 6s, perforate), or hagfishes, have the nostril highly 

 developed, a tube-like cylinder with cartilaginous rings pene- 

 trating the palate. In these the eyes are little developed and 

 the species are parasitic on other fishes. In Polistotrema stouti, 

 the hagfish of the coast of California, is parasitic on large fishes, 

 rockfishes, or flounders. It usually fastens itself at the throat 

 or isthmus of its host and sometimes at the eyes. Thence it 

 works very rapidly to the inside of the body. It there devours 

 all the muscular part of the fish without breaking the skin or 

 the peritoneum, leaving the fish a living hulk of head, skin, and 

 bones. It is especially destructive to fishes taken in gill-nets. 

 The voracity of the Chilean species Polistotrema dombeyi is equally 

 remarkable. Dr. Federico T. Delfin finds that in seven hours a 

 hagfish of this species will devour eighteen times its own weight 

 of fish-flesh. The intestinal canal is a simple tube, through 

 which most of the food passes undigested. The eggs are large, 

 each in a yellowish horny case, at one end of which are barbed 

 threads by which they cling together and to kelp or other objects. 

 In the California hagfish, Polistotrema stouti, great numbers of 

 these eggs have been found in the stomachs of the males. 



Similar habits are possessed by all the species in the two 

 families, Myxinida and Eptatretida. In the Myxinidcs the 



FIG. 291. California Hagfish, Polistotrema stouti Lockington. 



gill-openings are apparently single on each side, the six gills 

 being internal and leading by six separate ducts to each of 

 the six branchial sacs. The skin is excessively slimy, the ex- 

 tensible tongue is armed with two cone-like series of strong 

 teeth. About the mouth are eight barbels. 



