476 EDWIN S. GOODRICH. 



the Teleostei becomes obvious wlieu we consider tliat from 

 their first appearance the lepidotrichia in the anal and dorsal 

 fins correspond in number with the baseosts. The branching 

 of all dermal rays is most probably brought about in the same 

 way. As in the Elasniobranch_, so in the Teleost, the various 

 stages in the development of the dermal rays can be seen in 

 passing from the free edge towards the base of the fin. In the 

 Teleost, however, a second generation of lepidotrichia is never 

 produced. 



It will be understood from the above description that the 

 lepidotrichia succeed the actinotrichia, audare developed out- 

 side the latter; so that a section taken through the growing 

 edge of a fin, where both structures are present, invariably 

 shows the actinotrichia occupying the more internal region, 

 and the lepidotrichia between them and the epidermis. 



Harrison states that in Salmo the articulations of tlie lepi- 

 dotrichia are secondarily formed by the breaking through of 

 proliferating osteoblasts, which subsequently mould the joint 

 (13). This rupture of an originally continuous bony lamina 

 would occur very early in the development of the ray at its 

 growing end, where it is still quite thin. I venture to think 

 that this interpretation is not correct. My own observations 

 lead me to the conclusion that whilst, on the one hand, the 

 dei-mal ray may be said to be almost continuous — the articu- 

 lation being bridged over by softer, more elastic, and non- 

 calcified tissue, — yet, on the other hand, the joints are marked 

 out as soon as the ray becomes separated off from the base- 

 ment membrane. There appears to be no breaking of an 

 originally continuous hard piece; the osteoblasts migrate to 

 the outer side rather round than through the ray, and the 

 ai'ticulation becomes suddenly conspicuous owing to the 

 deposition of new outer layers of bony matter on each side of 

 the joint. At all events, I can affirm that joints appear at a 

 distance from the edge of the fin which is less than the length 

 of a complete segment of the dermal ray. 



It is clear that although the actinotrichia precede tlie 

 delinitive rays, and although they may occasionally become 



