1174 
SCANDINAVIAN FISHES. 
in batrachian larva? (fig. 344), a reminder that in their 
origins these two types were structurally not far re- 
moved from each other. The tongue of the Lampreys 
contains a long rod-like supporting apparatus, capable 
of protrusion and retraction, and suspended under the 
ceratohyal. This apparatus consists of two cartilages, 
an anterior, semipateriform, excised in front, situated 
in the mouth, and a posterior ( phy ), much longer, the 
posterior extremity of which projects into the branchial 
basket. It is interpreted as homologous with a basihyal, 
and the anterior cartilage bears the lingual teeth (tig. 
345), at the very tip a curved, transversal dental plate 
(aln), with firm, rounded and obtuse teeth, and further 
back two plates (pin), lying more loosely in the gums, 
meeting anteriorly in an ellipse, and furnished with 
small but acute, retral teeth. 
The whole oral apparatus of the Lampreys, which 
is abundantly supplied with cartilages, paired and un- 
paired, pateriform or lamellar and rod-like — one of 
Oc pro 
Ip pal spl hy fo Inn 
Fig. 344. Cartilaginous parts etc. in the head of a tadpole about 
1 in. long, at the time when the hind legs begin to appear. 
About 9 times nat. size. After Parker. 
ctr, n, and et, as in preceding figure; Eh, Thl, and Me, the three an- 
terior divisions of the brain; Oc, eye; als (alisphenoid), pro, (prootic), 
pto (pterotic), so (supraoccipital), eo (exoccipital), and op (opisthotic), 
all answering to t in preceding figure; dr, section of the skin; G, gill- 
opening; hr, as in preceding figure; hm and spl, answering to spl in 
preceding figure; fo, as in preceding figure; hy, answering to phy in 
preceding figure; Ip, lips (dermal flaps); mck, Meckelian cartilage; 
mdh, mandible; qu, quadrate bone; max, upper jaw. 
them annular — belongs to the extravertebral structures. 
Below the cornua trabecularum (fig. 343, ctr) is medially 
situated an invertedly pateriform cartilage (the median 
cartilage of the roof of the mouth, med, Muller’s “vor- 
dere Deckplatte des Mundes”), which has behind it on 
each side a flatly convex cartilage of a rounded quad- 
rangular form (the posterior lateral cartilage of the 
roof of the mouth, Ip, Muller’s “hintere Seitenleiste”) 
and at about the middle of its side-margin a narrower, 
more terete plate (the anterior lateral cartilage of the 
roof of the mouth, la, Muller’s “vordere Seitenleiste”). 
Under and before the said median plate lies the annular 
cartilage (ann, Muller’s “knorpeliger Lippenring”), the 
bearer of the largest teeth, which has behind it a me- 
dian plate (the sublingual cartilage, si, Muller’s so- 
called “Zungenbein”), situated under the tip of the hyoid 
bone, in front expanded and convex, behind acutely 
elongated. On each side of this sublingual plate lies 
behind the annular cartilage a rod-like cartilage (the 
lateral labial cartilage, lat, Muller’s u stielformiger 
Anhang cles Lippenring es")\ and three small cartilages, 
the bearers of the lateral teeth of the mouth, lie loosely 
in the skin on each side of the annular cartilage. 
The branchial basket (hr) too is entirely extra- 
vertebral, a network of thin flat cartilaginous rods, sup- 
porting the outer walls of the gill-sacs. Anteriorly this 
network is suspended from the epihyal cartilage; pos- 
teriorly the cartilaginous mass developes into a saccate 
case for the heart, a pericardial cartilage ( prc ). 
The nervous system of the Lampreys has thrown 
light, especially in two points, on the morphology of 
Fig. 345. Tip of the tongue and its dental plates in a Lampern 
(Petromyzon fluviatilis ), X about 5. 
aln, anterior dental plate of the tongue; pin, posterior dental plate 
of the tongue. 
the higher vertebrates. These points have reference to 
the interpretation of two organs still involved in great 
obscurity, the cerebral appendage and the pineal gland. 
At the bottom of the human cranial cavity, as well 
as on the under surface of the brain in all other true 
vertebrates, lies a glandiform organ whose function is 
still doubtful. It is known anatomically as the hypo- 
physis cerebri. In man it is about as large as a pea, 
oblong in form and transversally set, lodged in the de- 
pression on the upper surface of the sphenoid bone 
(the so-called sella turcica ) and attached to the brain by 
a funnel-shaped prolongation thereof in a downward 
direction from the bottom of the third cerebral ventricle. 
It consists of two parts, an anterior, the development 
of which we shall now describe, and a posterior, whose 
development originates from the brain. Great impor- 
tance was formerly attributed to it both by physiologists 
and psychologists. By Galen, in the second century 
