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EDWARD W. SHANN. 
atteution was called to the admirable paper by Mr. Groodrich/ 
which deals with the same question from the developmental 
point of view. The following is a summary, in his own words, 
of Mr. Good rich’s observations : ^ 
“ Besides these body-scales are found scale-like exoskeletal 
elements set end to end in rows and forming jointed dermal 
fin-rays, called lepi dotrichia, supporting the web of both 
the paired and the median fins. The minute structure of 
these fin-rays is almost or quite identical with that of the 
scales of the fish to which they belong. This is true more 
especially of the lower forms. In some, such as Amblypterus, 
there is a perfect gradation in form and arrangement between 
the body-scales and the fin-ray elements. But, as a I’ule, the 
transition is more abrupt, the segments of the rays acquiring 
a squarish or oblong shape, and not overlapping. Both the 
scales and the lepidothrichia are embedded in the dense con- 
nective tissue, the fibres of which enter the substance of the 
bone. Movable joints are formed by the fibrous matrix 
remaining unossified between them.” 
In the light of these facts, what had been but a passing 
idea acquired a real significance. The resemblance between 
a scale covered by connective tissue and a lepidotrich might 
easily be accounted for on grounds of analogy ; but since we 
know that fin-rays are developed from scale-like elements, it 
seems just to regard the fin-like scale of Sal mo as a con- 
necting link between a body-scale and a lepidotrich. 
The fin-like nature of the adipose lobe is enhanced by the 
fact that it is connected by a splint of bone with the ventral 
fin. What, then, is the homology of this bony splint ? We 
have noted that in the course of development it appears 
together with the lepidotrichia, which it resembles in structure, 
at a period before there is any trace of body-scales. Its 
position in the adult fish (p. 710), see fig. 2, indicates that it 
represents the doi-.sal half of an additional lepidotrich. If 
‘ Goodrich, E. S., “ On the Dermal Fin-rays of Fishes,” ‘ Quart. 
Journ. Micr. Sci.’ (v), vol. 47, 1903. 
- ‘ A Treatise on Zoology,’ Oxford, pt. ix, p. 212. 
