XV 
OBSERVATIONS ON THE DEVELOPMENT OF SOME 
PARTS OF THE SKELETON OF FISHES 
Quarterly Journal of Microscopical Science, vol. vit., 1859, pp. 33—46. 
THE following observations were made principally upon the 
Stickleback (Gasterosteus leturus) in 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 notochord 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— 
“TI 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 cartila- 
ginous fishes.” (p. 6.) 
The conception of a relation between the embryonic condition 
of the tail in Teleostean fish and the adult state of the same 
organ in Ganoided and Elasmobranchi, thus put forth, received a 
further development from Professor Vogt, the able author of the 
