THE LOWER VERTEBRATES 



153 



Augeri) is singularly inappropriate for blind animals ; the number 

 has been suggested by the seven breathing openings on each 

 side of the neck. Lamperns are often used for bait, and both 

 lamperns and lampreys are used for food. 



If a lamprey can be procured for demonstration there are 

 many interesting features to be made out, the scaleless slimy 

 skin ; the absence of paired fins ; 

 the two unpaired dorsal fins (in 

 the young forms continuous with 

 one another and with the tail-fin) ; 

 the circular suctorial mouth and 

 the piston-like muscular " tongue " 

 (not in the strict sense a tongue), 

 both beset with horny teeth ; the 

 unpaired nostril far back on the top 

 of the head, like the blow-hole of 

 toothed whales ; the seven pairs of 

 gill-clefts, and so on. 



In some parts of Britain, e.g. on 

 the coast of Northumberland, it 

 may be possible to get from the 

 fishermen a specimen of another re- 

 markable Cyclostome the glutin- 

 ous hag Myxine glutinosa. It is 

 an eel-like pinkish animal, from 15 

 to 24 inches long. It lives in deep 



water, often at a depth to which the light hardly penetrates. 

 With this, and with its habit of burrowing in the mud, 

 we may associate the absence of pigmentation in the skin 

 (the pinkness being due to the red blood shining through), 

 and the fact that the eyes are vestigial and do not reach the 

 surface. It can swim gracefully and rapidly in eel-like fashion 

 in search of prey, but so far as we know it seems to live a some- 

 what sluggish life. It eats the bait of the fisherman's long lines, 

 and it sometimes enters and devours the cod, etc. which have 

 been caught on the hooks. There is a piston-like "tongue," 

 as in the lamprey. According to some, the hag also bores its 

 way into free-swimming fishes, but the evidence is not satis- 



FIG. 56. The funnel or porch to the 

 lamprey's mouth. It has numerous 

 horny teeth above and below the 

 mouth proper (./., upper teeth ; /./., 

 lower teeth). The funnel is applied 

 to the lamprey's victim, and adheres 

 like a vacuum sucker. The toothed 

 piston (p\ often called the tongue, 

 works as a boring instrument, rasp- 

 ing off the flesh. Behind the funnel 

 there is a hint of the eyes slightly 

 protruded ; their position is indicated 

 on the preceding figure. 



