408 Abhandluityeii der Koniylichen 
1. A filamentous cartilaginous tube filled with gelatinous matter, and sur- 
rounded with a fibrous skin, the upper side of which forms a second tube, rest- 
ing on the lower, and which is occupied by the spinal marrow. No rudiments of 
bone or divisions into joints. The Myxinoidea and Ammoccetes. 
2. The same structure as the former, except that on the upper part of the 
tube there are some cartilaginous processes. Petromyzon. 
3. The same structure as the last, with the addition of two cartilaginous ba- 
silary processes placed on the under side of the spinal column. Accipenser, Po- 
lyodon, Chimaera. 
4. The gelatinous tube remains constant, and portions of a fluid gelatinous 
substance occur between the conical facets of the spine, which articulate with 
one another. The joints of the spine developed. Fish, Protese, Menopome, Cae- 
cilia, and the young of frogs and salamanders amongst the naked Amphibia. 
(Foetus of the higher animals at one period of their growth ?) 
5. The conical facets of the joints of the spine, and the gelatinous matter be- 
tween them remain stationary, and the spine is either simply divided into joints, 
( Amphibia, birds during their growth,) or has ligamenta intervertebralia between 
them. Mammalia, Man. 
The author then proceeds to compare the cranium of the Myxine with that of 
the Petromyzon, and in the following chapter, he compares the cranium of each 
with the structure of their respective spinal columns, and with the skulls of the 
Embryos of the higher animals. He describes the gradual development of the 
skull as we ascend from the lower classes of vertebrata, and considers the crania 
of Ammoccetes and Myxine to be analogous to those of the foetus of the higher 
animals. 
He next describes the labial cartilage, and remarks upon the great variety in 
the formation of the lips in this class of fishes, as well as the different number 
of lips possessed by various genera, and the uncertainty they have caused amongst 
authors. The palateal bones and those of the jaws are next described, beginning 
with the Plagiostomata, and proceeding through the different families down to 
the Cyclostomata. He then continues his account of the comparative anatomy 
of the remaining bones of the head, except those of the tongue and the branchiae, 
which in the generality of the cartilaginous fishes, as those of the Myxinoidea, vary 
too much from them to admit of comparison. Their structure, moreover, has al- 
'ready been well described by Rathke and Henle. Having thus concluded the osteo 
logy of the Cyclostomata, the author proceeds to describe their Myology, and 
follows the same plan as before, in first giving the details of their muscular sys- 
tem, and then their comparative anatomy. The descriptions are illustrated by 
very accurate plates engraved from the author's drawings, without which it is 
impossible to give an intelligible notion of the various structure in a mere ana- 
lysis like the present. The muscles of the trunk are first explained, and then 
those attached to the various bones of the head, and lastly, those of the tongue, 
which in the Myxinoidea have no resemblance to those of other animals. The 
organs of breathing in the Bdellostomata and the Myxine glutinosa are then de- 
tailed, and the various muscles of the different genera compared with one an- 
other ; and lastly those of the trunk, with the corresponding ones in the higher 
orders of animals. The remainder of the treatise is occupied by a curious dis- 
sertation on the analogy of the muscles in different parts of the human body, and 
on the variations observable in different individuals, as well as in animals, such 
