CHAPTER LXIV 

 THE LOWEST CLASSES OF VERTEBRATES 



There are a few creatures which, by reason of 

 their internal skeletons and jointed back-bones, 

 are justly entitled to stand with the vertebrates, 

 but yet are lower in the scale than the lowest 

 fishes. For these it has been necessary to create 

 two grand divisions of the first rank; and they 

 stand as two small and very low Classes. It is 

 because of their very low position in the zoological 

 scale of vertebrates that it becomes important to 

 know them. 



THE LAMPREYS. 



Class Marsipobranchii. 



A Lamprey is an aquatic creature which bears 

 so strong a resemblance to an eel that for a long 

 period all lampreys were regarded as true eels. 

 Even to-day, the most important of our species 

 is, by unscientific persons, almost universally 

 called the "Lamper Eel." In view of the gen- 

 eral external resemblance of these creatures to 

 eels of similar size, it is not strange that their true 

 character remained for a long period quite un- 

 known. As a matter of fact, these creatures for- 

 cibly illustrate the unwisdom in animal classifica- 

 tion of attaching too much importance to external 

 characters. 



The lampreys are the lowest and last creatures 

 that have the spinal cord expanded at its upper 

 end into a brain, and encased in a skull. But the 

 skull is imperfectly developed, and without jaws; 

 there is no shoulder girdle, no pelvis, no limbs, no 

 ribs, and no paired fins. There is a single median 

 nostril, the gills are purse-shaped, the skin is naked 

 like that of an eel, and the skeleton is cartilaginous. 

 The gills are in the form of a fixed sac, the gill open- 

 ings consist of a row of tiny round holes along 

 the side of the body, and the mouth is specially 

 formed for suction. 



It is evident from the foregoing characters that 

 the lampreys are creatures of very simple form, 

 lacking almost all the evidences of special develop- 

 ment which characterize the higher fishes. Ex- 



ternally, their very modest median fins are the 

 only visible signs that they are not marine worms. 



The Sea Lamprey 1 is the best and most avail- 

 able example of the Class Mar-si-po-branch'ii. 

 "The mouth is completely circular, and forms a 

 great and powerful sucker, surrounded by fleshy 

 lips that are supported on a framework of cartilage 

 and studded with tentacles. This mouth is cov- 

 ered over its entire interior surface with strong 

 teeth arranged in concentric circles. A large 

 double tooth, situated above the aperture of the 

 mouth, indicates the situation of the upper jaw, 

 and seven or eight great teeth represent the lower 

 jaw. Even the tongue carries three large teeth, 

 deeply serrated on their edge." 2 



With a mouth specially formed and savagely 

 equipped for suction, it is no surprise to find that 

 this creature is a blood-sucking parasite, preying 

 upon other forms of marine life. It is often found 

 attached to shad, sturgeon, sharks, cod, halibut 

 and mackerel. It fastens to its victim beneath 

 the pectoral fins, tears at its flesh with its rasping 

 circles of teeth, and sucks its blood "until the 

 flesh becomes as white as paper." Beyond doubt, 

 these creatures destroy a very considerable num- 

 ber of valuable food fishes. Fishermen charge 

 to the account of the Lamprey the raw spots and 

 sores frequently found upon the bodies of stur- 

 geons. 



Formerly the Lamprey was greatly esteemed 

 by the people of Massachusetts as a food "fish." 

 In the Merrimac River it was captured in great 

 numbers, and salted down for winter use. 

 While this industry, and its object, have both 

 greatly decreased, in some portions of Connecticut 

 the Lamprey is yet taken, as often as it can be 

 found, and thankfully consumed. The species 

 specially mentioned varies in length from two to 

 three feet, but the Brook Lamprey, and all the 



1 Pet-ro-my'zon ma-ri'nus. 



2 " Fishery Industries of the United States," 

 Part I, p. 677. 



437 



