92 General Notes. [January, 
Parker). After the absorption of the lophocercal tail of anurous 
amphibian larvæ has been in progress for some time, it seems to 
Fig.2 
tend to lose its median folds somewhat and revert to the archicer- 
cal condition. This is also the case with the young of most 
Urodela as they approach maturity. 
2. Lophocercy—The second stage of development of the median 
fin-system of Ichthyopsida is what I have called /ophocercal 
(= protocercal, Wyman; = /eptocardial, A. Agassiz) when it con- 
sists of continuous folds (Amphibia, Elasmobranchs, Teleosts, 
etc.), or exceptionally of discontinuous folds (Siphostoma, Gam- 
busia) which do not include permanent rays. The continuity of the 
median fin-fold in young fishes seems to depend somewhat upon 
the extent to which the permanent fins are approximated in the 
adult. Several forms amongst the Clupeoids develop an ex- 
panded eradiate caudal fold, with the chordal axis dividing it into 
equal moieties, which anticipates the form of the outwardly homo- 
cercal tail of the adult. At the close of the lophocercal condition 
the ray-bearing fishes at once diverge from the rest of the Chor- 
data, and also the Urochorda, in that they develop embryonic rays 
in definite regions of the median fin-fold or continuously through- 
out its entire extent and which give rise to the rays of the dis- 
tinct or continuous fins of the adult. The intervening parts of 
the fold in the first case atrophy (—local reversion to archicercy), 
Fig. 3. 
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the materials for the formation of the rays being supplied par- 
tially by mesoblastic secretion, while the axial parts are of meso- 
blastic origin; the materials for the medulla of the rays being 
supplied by the outgrowth of mesoblast into the fold. The dis- 
position of the materials for the development of the rays of the 
unpaired fins seems to be very decidedly under the control of 
heredity, which determines their permanent location or position in 
E a NE ge 
