184 Records of the Indian Museum. [Vor. XVilly 
specimens it is considerably less. The fin is strongly compressed 
from side to side. 
In vertical section an external wall and an internal core can 
be distinguished. The former is further divided into two regions, 
an external epithelial and an internal connective-tissue region. 
The epithelial region, which is similar to the integument of the body, 
consists mainly of several layers of small, more or less flattened 
and rectangular cells with well-defined cell-walls and relatively 
large oval nuclei. Among these are scattered numerous large 
ampulliform gland-cells. In the lower parts of the fin the gland- 
cells are situated mostly at the base of this-+region and constitute 
almost a separate layer, the small epithelial cells between them 
being somewhat elongated by pressure. ‘Towards the crest of the 
ridge, however, there is no definite separation of the kind and the 
gland-cells are often on the surface. 
The inner region of the outer wall consists of fibrous connec- 
tive tissue, the fibres of which run completely round the fin in 
a horizontal and vertical direction, separating it below from the 
dorsal muscles, over which the epithelial layer does not extend. 
This region is similar to that lying immediately below the 
epithelial covering of the body. 
In the region of the connective tissue and between it and that 
of the epithelium numerous longitudinal blood vessels can be easily 
distinguished. They have a narrowly oval outline in vertical 
section, with the longer axis vertical in the side-walls, and trans- 
verse above the dorsal muscles. : 
Just inside the region of connective tissue of the side-walls 
there are a number of small lucunae containing granular masses of 
black pigment. These have no definite walls. 
The central core consists of a mass, conical in vertical section, 
of highly vacuolated tissue. ‘The vacuoles are of relatively large 
size and irregular shape. No cell-walls can be distinguished but 
the spaces are surrounded by deeply staining protoplasm contain- 
ing numerous minute oval nuclei. The contents of the vacuoles 
are gelatinous and appear to havea reticulate structure when 
stained with haemotoxylin. This structure, however, may be an 
artifect. 
Comparatively large blood-vessels make their way obliquely 
upwards from the body into the central core of the soft fin at 
intervals and ramify in it. We have not been able to trace any 
connection between them and the smaller lateral and basal 
vessels. 
In the upper part of the fin irregular fibrous strands, probably 
representing degenerate ceratotrichia, can be distinguished in the 
centre of the core. They run ina vertical direction, and are 
connected with a kind of reticulation formed by the walls of the 
vacuoles. 
In external appearance the adipose fin of Adiposia closely 
resembles that of the soft fin of the Siluroid genus Amblyceps, 
which is assigned by recent authors to the family Sisoridae. We 
