THE 
ADIPOSE LOBE OP 
THE PELVIC 
PIN UP THE SALMON. 719 
No. 
Age. 
Length.* 
Condition of adipose lobe. 
1 . 
5 weeks 
23’5 inm. 
No trace externally 
2 . 
6 
25 ., 
• ? > ) ) 
3 . 
7 
24 
4 . 
8 ,, 
24 ,, 
• . » ) ) 
5 . 
10 , 
24-5 ,, 
• ♦ » ? ) 
6 . 
12 ,, 
26‘5 ,, 
• •> J> 
7 . 
14 , 
27 „ 
• ; ’ ; ) 
8 . 
16 ., 
29-5 ,. 
9 . 
19 ,, 
34-5 .. 
Very slight papilla 
10 . 
21 „ 
41 
Slight projection 
11 . 
23 ,. 
43-.5 ,, 
Distinct lobe 
* From tip of lips to fork of tail. 
The specimens were fixed in Zenker’s fluid. Transverse 
slices comprising the whole of the pelvic region were cut from 
each fish. These slices were embedded in paraffin, remaining 
in the oven for 1 i to hours, according to their size, and 
stained in hfematox}din (Grenadier^) on the slide. 
(1) Description of the Sections. 
In the youngest fishes examined (Nos. 1, 2 and 3) the splint 
makes its appearance in the series as an ossified strand, 
lying just beneath the surface in the upper angle of the 
fin-fold, and on a level with tlie plane which divides the two 
adductor muscles. Passing over a few sections in the posterior 
direction the head of the dorsal half of the first lepidotrich 
comes into view at the outer end of the b as ale and between 
the two adductor muscles; the splint in the same section is 
seen to be travelling ventralwards and outwards. Slightly 
beyond this again the splint is seen to come into close contact 
with the haft of the dorsal half of the first lepidotrich, so that 
the two together form a V-like structure of bone, lying in the 
dorsal region of the developing fin, with the angle of the V 
pointing towards the fin’s proximal extremity. In the section 
last__described the basale is still quite entire, and there is 
‘ ‘ Practical Zoology,’ Marshall and Hurst, ed. vi, p. 466. 
