July 1, 1S69.] 



HAKDWICKE'S SCIENCE-GOSSIP. 



147 



proach the centre of the cavity of the mouth. The 

 converging series in the mesial plane are arranged 

 in a straight line, those of the sides in curved lines 

 with the concavity towards the lower margin of the 

 mouth ; in P. marbms the innermost teeth of four 

 of the lateral series on each side are bicuspid, or 

 consist each of two cones which are confluent at the 

 base; there are twenty converging rows of teeth in 

 this species, and from four to eight teeth in each 

 row. The single tooth supported by the palatal 

 cartilage consists of two horny cones placed in the 

 transverse direction, and joined (in P. marinus) in 

 the median line; but in the Lampern (P '. fluviatilis) 

 the cones are more remote. The matrix of this 

 tooth is hollow at the base, and is supported on a 

 conical process of the palatal cartilage, which 

 Cuvier describes as the upper jaw. The broad bi- 

 cuspid palatal tooth is opposed by the dentated, 

 semilunar, horny plate with which the cartilage 

 representing the lower jaw is sheathed. This plate 

 consists of eight conical teeth, laterally united to- 

 gether. The lingual teeth consist of three dentated 

 horny plates, the dentations being much smaller 

 than in the palatal or mandibular plates." 



It has been asserted that when the Lamprey at- 

 tacks a fish, it first drives the large palatal tooth 

 into the flesh of its living prey, and holds on there- 

 by as by a grappling-iron, while it applies its suc- 

 torial mouth gradually in a leisurely manner. Now 

 this palatal tooth being the farthest back in the 

 creature's mouth, almost at the entrance of the 

 throat, cannot by any possibility be the first to reach 

 the side of the fish attacked, nor is it of sufficient 

 size and strength or sufficiently recurved to be 

 capable of performing this special office : the edges 

 of the lips are of necessity (as any one may assure 

 himself by experiment) first brought in contact with 

 the surface to which the animal wishes to affix it- 

 self; the tongue is probably retracted instantaneously 

 and a vacuum formed. The hold secured by such 

 means must be very powerful. Some of our young 

 friends may amuse themselves by calculating the 

 atmospheric pressure on the external surface of a 

 sucking disc two and a half inches in diameter, 

 which will give them some idea of the power of 

 adhesion possessed by the Lamprey, even supposing 

 that the teeth are not brought into play at all. 

 There can be little doubt that the Lamprey can 

 fasten itself as instantaneously to the side of a fish, 

 as we know it does to a stone or to the bottom of a 

 boat by means of its lips ; how the teeth act after the 

 lips are glued to the prey, must be very much a matter 

 of conjecture, as they are then altogether invisible ; 

 whether the trephine-like saws of the tongue which 

 seems capable of turning every way, or the entire 

 armature of the mouth is used, no one can tell with 

 certainty ; but we know that by some process of 

 sawing, rasping, and grinding, the fierce pirate 

 (without inflicting mortal injuries) contrives to tear 



away and swallow mouthfuls of mashed-up flesh 

 like forced-meat balls, from the bones of its hapless 

 and vainly struggling victim, releasing it after the 

 cannibal meal is over. Eish which have had toll thus 

 levied on them are often caught, apparently not 

 much the worse for the operation. 



Fig. 114. Respiratory Apparatus of the Lamprey, one-third of 

 the natural size. 



In this figure, which is reduced from a plate by 

 Sir Everard Home in "Philosophical Transactions," 

 (a) represents the tongue, which with the dentated 

 semilunar plate (p) is turned on one side ; (b) the 

 cavity of the mouth ; (c) the fauces ; (d) the bran- 

 chial channel or tube into which the gill-chambers 

 open ; (e) the termination of the same channel in a 

 so-called "loose-edge" (?) at the origin of the 

 oesophagus ; (f) a firm cartilage in the centre of the 

 retractory muscle of the tongue ; (g, g) two large 

 salivary glands ; (h, h) the cavities containing a 

 structure like gills, laid open through their whole 

 extent ; (i, i) external orifices of the gill-cavities ; 

 (k, k) their internal orifices opening into the 

 branchial tube ; (/, I) cartilages of the thorax ; (m) 

 the cartilaginous case containing the heart (ac- 

 cording to Owen, " the pericardium is a shut sac, 

 supported by a perforated case of cartilage formed 

 by the last pair of modified branchial arches ") ; (n) 

 termination of the oesophagus in the stomach. The 

 process of respiration is thus briefly described by 

 the writer from whose monograph the preceding 



h 2 



