Dkumoptekes.- 



-FISIIES.- 



-Pethosivzontids. 



Ill 



support the large tooth-bearing tongue. When a 

 Myxinoid or a Petromyzontid is preserved in spirits, 

 the teotli readily flake off in cap-shaped layers, leaving 

 a comparatively soft, conical nucleus, and furjiishing 

 evidence of the rauoo-dennoid origin of these organs in 

 the Dermopteres. The arrangement and form of the 

 labial, palatine, and lingual teeth of the different Petro- 

 myzontids supply the generic characters of the various 

 groups that compose the family. One Australian genus 

 {Gcotria) has a remarkably large guttural pouch before 

 the gill-openings, corresponding to the rudimentary 

 dilatation of the same part in the common Marine 

 Lamprey, and having an external resemblance to the 

 goitre of the iguana. 



The single mesial nostril-tube of the Dermopteres 

 is flask-shaped in the Lamprey, and descends to the 

 base of the skull, but is there closed by the imperforate 

 mucous lining of the palate, differing in that respect 

 from the naso-palatine tube of the myxinoiils, which 

 terminates by a valvular opening on the roof of the 

 mouth. In the Lampreys, the eye-ball is suppilied 

 witli muscles for effecting its various movements, which 

 are wanting in the rudimentary optic organs of the 

 rayxinoids ; and, on the other hand, the acoustic cap- 

 sules are less conspicuous on the base of the skull than 

 in myxine, such prominence being an embryonic 

 character. There is also a greater extension of the 

 organ of hearing of the Lampreys into a membranous 

 vestibule, a feitestrum, or as Breschet names it an 

 aqueduct, and an accessary sinus, but there are neither 

 semicircular canals nor otolites. The author just 

 named, considers the oi'gan of hearing in the Lam- 

 preys to have a stronger resemblance to that of the 

 crustaceous or cephalopode molluscs, than to the 

 acoustic apparatus of osseous fishes.* None of tlie 

 Dermopteres present a greater development of the 

 hyoid apparatus, than that which consists in the presence 

 of a lingual cartilage, and some ligamentous bands 

 which we shall notice below, as existuig in the larval 

 state of some members of the group. 



A small Dermoptero, inhabiting the streams fre- 

 quented by the Lampreys throughout Europe, and 

 known in England under the various names of Prid, 

 Pride, Sandpride, Sandburker, Stonegrig, and Mudlurker, 

 was ascertained b)' Auguste Miiller some few years ago, 

 to be merely a larval condition of the Fringed Larapern. 

 Its eyes are so small, that it was named tlie Blind 

 Lamprey by the distinguished British naturalist Kay; 

 and its mouth, instead of being circular, has a horse- 

 shoe shape, and cannot act as an adhesive sucker ; 

 but the rudiment of a future suctorial musclo is per- 

 ceptible in it. Keither is the pharyngeal inspirator}' 

 tube as yet distinct from the oesophagus, and the gills, 

 instead of being wholly adherent to the walls of the 

 gill-chambers, have their tips free. This part of the 

 structure is an approach to the free gills of the osseous 

 fishes, and is suited, doubtless, to the free non-parasitic 

 habits of the larva or ammoccete — so the young Lam- 

 preys are now called; the appellation having been taken 

 from the generic name Ammococtes, given when the fish 

 was supposed to be a distinct species, and which is trans- 



• See Itecherches sur I'organe de L'ouie des roi^ous par 

 G. Breschet. Taris, 1838. 



lated " mud-lurker." In the ammoccete, then, each gill- 

 sac communicates directly with the pharynx, and opens 

 on the side of the neck, as we shall hereafter show to 

 be the case in the Selachians. No teeth are formed in 

 the mouth of the amniococte, but very early in its 

 life a valve is developed within the mouth, which 

 allows the water to enter, but prevents its reflux ; and 

 this muscular membrane is fringed so as to act as a 

 strainer out of noxious particles. Tlie food of the 

 Pride consists chiefly of infusorial animalcuke (Bacil- 

 laria). Auguste Miiller watched Lamperns in the 

 act of spawning, secured the roe, kept it under obser- 

 vation until it was hatched, and afterwards carefully 

 observed the larval or ammoccete life of the 

 fish. In the fourth year of its existence, he saw the 

 transformation to the adult form begin, and go on to 

 completion in the com"se of ten days. There is no 

 increase of size, but in that time the respiratory 

 phai-yngeal tube is formed, teeth are evolved, the valve 

 or velum in the mouth disajipears, the intestinal canal 

 is sensibly abbreviated, and the roe which was pre- 

 viously transparent, becomes opaque. This transfor- 

 mation, though not so remarkable externally as that 

 which occurs in the Tadpoles, was, previous to Auguste 

 Mliller's time, unsuspected in the class of fishes. The 

 facts he have stated, has been testified too by other 

 observers; and the Ammoccctes, not only of the Fringed 

 Lampern, but of other European Lamperns and Lara- 

 preys have been detected.* 



The following genera compose the Petromyzontid family : — 

 Pttvomtjzon, Lanipf^tj'a, Geotria, Velctsia, Curayola, and JA/r- 

 tlacla, all of which are characterized by Dr. Gray in one of his 

 catalogues of the Fishes in the British iluseum. 



THE LAMPREY [Petromyzon marinus) — Plato 1, fig. 

 2 — is the species best kno^vn, and the only one so far 

 as we know, that is used in Eiuope as food. It is 

 said to be a highly esteemed fish for the table in the 

 United States of America, and has long been held 

 to be a delicacy in England. Henry I. is said by 

 Matthew of Paris, to have died, in 1135, at St. Denis 

 le Ferment, of a sudden illness occasioned by eating 

 too plentifully of lam]ireys, as the poet Pope is reported 

 to have done in more recent times ; and Henry IV. 

 is stated by Pennant, quoting from Rymcr's Fcedera, 

 to have granted protections to such ships as brought 

 over lampreys for the table of his royal consort. 

 Henry VI. contracted with Wflliam of Nantes for 

 a supply to his army, whithersoever it might march, 

 of lampreys to be taken between the mouth of the 

 Seine and Ilarfleur. It was anciently a custom of 

 the city of Gloucester, to present the British sovereign 

 with a lamprey pie. Camden, speaking of the lam- 

 preys of the Severn, says, that they are finest in the 

 spring, being then more tender, and that, in his time, 

 the Italians prepared them for the table by drowning 

 them in Cretan wine, placing a nutmeg in the mouth 

 and a clove in each gill-opening, rolling them up 

 spirally in the flour of filbert-nuts and crumbs of 



* Dr. M. S. Schultze has written still more recently on tlie 

 eariy life of Fctronvjxon I'lancri \\\> to si.x weeks after its 

 exclusion from the egg. At that age the small eye is buried 

 under the skin, and tlie oval velum of the ammocoste is present 

 instead of a separate respiratory tube, so that thus far tho 

 memoir confirms Auguste Mailer's observations. 



