33 
OBsERVATIONS on the DrveLopmMentT of some parts of the 
SKELETON of Fisues. By Tuomas H. Huxtey, F.R.S., 
Professor of Natural History, Government School of 
Mines. 
Tue following observations were made principally upon 
the Stickleback (Gasterosteus leiurus) i the summer of the 
present year. Some of them were briefly alluded to in my 
Croonian lecture “On the Theory of the Vertebrate Skull,” 
delivered before the Royal Society on the 17th of June 
last, and will be more fully treated of hereafter; the rest 
have not yet been published. 
1. On the development of the tail in Teleostean fishes. 
The fact that at a certain period in the embryonic life of 
Teleostean fishes, the extremity of the chorda dorsalis or noto- 
chord is bent upwards, was discovered and its importance 
indicated by K. E. Von Bar, in his ‘ Untersuchungen iiber 
die Entwickelungs-geschichte der Fische’ (1835), where 
he remarks, respecting the embryos of Cyprinus blicca— 
“‘T was greatly surprised to observe, that from the fifth 
day onwards, the posterior extremity of the vertebral column 
bends upwards, so that the caudal fin which now begins to be 
developed is not disposed symmetrically, but lies more below 
the extremity of the vertebral column; a relation which is 
permanent in the cartilaginous fishes.” (p. 6.) 
The conception of a relation between the embryonic con- 
dition of the tail in Teleostean fish and the adult state of 
the same organ in Ganoidet and Elasmobranchii, thus put 
forth, received a further development from Professor Vogt, the 
able author of the ‘ Embryologie des Salmones’ (1842), which 
forms a part of M. Agassiz’s ‘ Poissons d’Eau douce.’ At 
p. 256 of this excellent monograph, Vogt says— 
“The curvature of the extremity of the chorda dorsalis, 
which begins to be apparent in the Coregonus a short time 
before it is hatched, and attains its greatest amount about 
six weeks later, is another peculiarity of the embryos which 
deserves to be taken into consideration, because it subse- 
quently disappears, and exists in adult fishes only in some 
genera of existing Ganoids and Placoids. These relations have 
not escaped the notice of observers, and M. Von Bar par- 
ticularly expresses himself as follows.” 
Vogt here gives the preceding citation from Von Bar, 
and then continues : 
