MYXINOIDS OR HAG-FISHES 443 



A very valuable contribution to our knowledge of the habits 

 of Myxinoids was made by Julia Worthington (" Contri- 

 bution to our Knowledge of the Myxinoids," American Natu- 

 ralist, xxxix., 1905, pp. 625-663) who had the good fortune 

 to obtain several hundred individuals of Bdellostoma dombeyi 

 Lac. of the Pacific Coast, and to succeed in keeping them in 

 good condition in an aquarium. Some of the results of four 

 months' observation may be summarised ; they afford a good 

 illustration of the study of habits. 



The Pacific hag, which abounds in the Bay of Monterey, is 

 usually found at a depth of about 50 fathoms, particularly on the 

 rock -cod beds. In the aquarium, they preferred a hard bottom, 

 and were fond of lying coiled among the rocks. " When well 

 and at rest, the hag-fish is invariably coiled up more or less 

 tightly, either in a spiral by itself, or in and out among the 

 rocks. But if exhausted or sick, the coil straightens out, and 

 it lies in a crescent form. The sicker it is, the straighter it be- 

 comes, and when dead it lies entirely straight." They are ex- 

 tremely sensitive to rise of temperature, though they are very 

 hardy animals in most respects. 



The habits of the European Myxine glutinosa are some- 

 what different. Mr. J. T. Cunningham in the years 1884- 1886 

 kept numbers of specimens of this species in tanks with mud at 

 the bottom, at Granton on the Firth of Forth near Edinburgh, 

 and found that the animals always burrowed into the mud and 

 remained quiescent in the daytime, with only the tip of the 

 snout exposed. At this point is situated the naso-pituitary 

 aperture, and the current of water entering this and escaping 

 at the single pair of exhalent apertures further back could be 

 clearly seen from the movement of particles of mud. As the 

 Myxine were taken on muddy ground at a depth of about 40 

 fathoms, off St. Abb's Head, there can be no doubt that it is 

 their natural habit to burrow into the mud. The difference of 

 habit in the two cases probably corresponds to the difference 

 in the exhalent gill-apertures, between Myxine and Bdellos- 

 toma, the former having a single aperture on each side, the 

 latter a separate aperture for each gill-pouch. 



Hags swim swiftly, with a graceful serpentine motion, but 

 they prefer a quiet life, especially during the day. The muscle 

 segments or myotomes alternate as they do in lancelets. 



