THE ADIPOSE LOBE OP THE PELVIC FIN OF THE SALMON. 711 
iiinei’ aspect} of tlie latter, however, near the proximal 
exti’emity, there ai*e certain masses of tough ligament [Ug-), 
which unite it with the heads of the dorsal halves of the first 
(outermost) and second fin-rays. Owing to this arrangement 
a certain amount of movement of the adipose lobe is conse- 
quent to the movement of the fin-rays, but there appears to 
be no mechanism for independent action. Further dissection 
of the lobe revealed the presence of an irregularly shaped 
mass of hard substance running throughout its length ; near 
the base the mass is more or less spear-shaped, so that it 
appears linear in cross section ; as the distal exti’emity is 
approached the section becomes triangular, but in all parts a 
flat surface runs parallel with, and close beneath, the vertical 
outer wall of the lobe. 
(3) Histology of the Adipose Lobe. 
Transverse sections, taken near the base of the lobe shortly 
before it loses all connection with the body-wall, are tri- 
angular in outline. Fig. 3 represents such a section together 
with the adjacent portion of the body-wall. The first feature 
of note is the entire absence of epidermis, not only on the 
surface of the lobe, but also on the surface of the opposing 
body-wall; this condition invariably obtained in the case of 
all adult specimens examined by me.^ The lobe is bounded 
by a sing’le strand of homogeneous material, which is slightly 
refriugent and stains deeply with iron-h^matoxylin ; this 
strand I take to be the membrana basale {M.h.). Below 
the membrana basale the lobe is composed of dense 
connective tissue {C.t.), whose fibres run approximately 
' It should be mentioned, however, that the fish had all travelled con- 
siderable distances before they reached me, so that the epidermis may 
have been rubbed off during transit or may have decomposed during 
the time that elapsed before the tissues were placed in the preserving 
fluid. I hope later to have an opportunity to clear this doubtful 
point by preserving carefully the adipose lobe from a salmon immediately 
it is taken from the water. 
VOL. 58, PART 4. NEW SERIES. 
47 
