470 CYCL0ST0MATA. 



the bait off the fisherman's long lines, and it also enters and 

 devours the cod, etc., which have been caught on the hooks. 

 According to some, the hag also bores its way into free- 

 swimming fishes, but the evidence is not satisfactory. Mr. 

 J. T. Cunningham discovered that the young animals are 

 hermaphrodite, containing immature ova and ripe sper- 

 matozoa, while older forms produce ova only ; and Nansen 

 has corroborated this. A somewhat similar " protandrous " 

 hermaphroditism is known elsewhere, e.g. in the Nemertean 

 Stichostemma eilhardii, in the aberrant Myzostoma, and in 

 the crustacean Cymothoidae. Of the development and 

 early history nothing is known. They are said to spawn in 

 late autumn. 



Form, skin, and muscular system. — The body is eel- 

 like, measuring 15 to 24 in. in the adult. The colour is 

 pinkish, the red blood shining through an impigmented 

 skin. There is a slight median fin around the tail ; beside 

 the mouth and nostril there are four pairs of sensitive 

 barbules. There are no paired fins. The cloacal opening 

 is near the posterior end of the body. 



The skin is scaleless, and rich in goblet cells, which 

 secrete mucus. There is also a double row of glandular 

 pits, partly embedded in muscle, and arranged segmentally 

 on each side of the ventral surface along its entire length. 

 Each opens by a distinct pore, and so much mucus is rapidly 

 secreted that the ancients said the hag " could turn water 

 into glue." This makes the hag difficult to grip, and its 

 function is doubtless in part protective. The mucus chiefly 

 consists of strange spiral " thread cells," ejected from 

 the sacs. 



The muscle segments or myomeres are to some extent 

 traceable. The rasping teeth are worked by a powerful 

 muscular structure, sometimes called a " tongue." A 

 section of this shows a strong muscular cylinder surrounding 

 a cartilage. 



The skeleton. — The skeleton is wholly cartilaginous. 

 The notochord persists unsegmented within a firm sheath, 

 the skull is a simple unroofed trough, jaws are not 

 distinctly developed, there is only a hint of the complicated 

 basket-work which supports the gill-pouches of the lamprey ; 

 but the tongue, the barbules, etc., are supported by cartila- 



