On the Structure Of The Eel's Skull

Abstract

THE skull of the Eel is much less specialised than that of most other Osseous (Teleostean), fishes. I was made aware of this many years since whilst preparing skeletons of the common kind (Anguilla acuiirostrzs), and of the conger (Murccna conger). Afterwards, when Prof. Huxley's “Croonian Lectures”(Proc. Roy. Soc.) came into my hands, the importance of the aberrant structures of this type of skull was shown to me; and since that time I have been on the watch for further opportunities for dissecting and working out both this type, and also that of the Amphibia, which it serves to illustrate. In a few weeks' time I shall be able to make myself understood with regard to those morphological changes which take place in the vertebrate skull as it passes from a low Ichthyic into the higher Amphibian type. This will be done by the illustration and description of the frog's skull in the forthcoming part of the “Philosophical Transactions,”an abstract of which paper has already appeared in these columns. At present the nomenclature of the parts of the cranium and face of the fish is in a state of painful confusion. I shall not, however, trouble the student with confusing references, but continue to use those terms which he will find in my other morphological papers. I may, however, remark that these differ in some instances from those used by Professor Huxley, for instance, his “squamosal”is my “pterotic”(see “Elem. Comp. Anat.,”p. 188). This is a bone called “mastoid”by Cuvier, and this term was adopted by Prof. Owen. These anatomists came much nearer the truth than my friend; but the bone only represents part of the human “mastoid” —its anterosuperior region. Again, the terms for the palato-pterygoid arcade are very confusing; Cuvier's “internal pterygoid,” also called ento-pterygoid by Owen and Huxley, does not correspond to the internal pterygoid plate of man and the mammalia generally, but to a third piece, which I call meso-pterygoid, and which occurs in a young-pig's and in a young fox's skull in my collection; I have also found it in the palate of all sorts of birds, except the fowls and Struthionidæ. The true representative of the human internal pterygoid is, in fishes, called “transverse” by Cuvier; most correctly the “pterygoid” by Owen; confusingly the “ecto-pterygoid” by Huxley. I drop the frequently misapplied terms, “ecto” and “ento-pterygoid,” altogether, and call the true “transverse bone” of the reptile—never seen in fishes—the “transpalatine.” Most of the other terms used by me agree with those used by Prof. Huxley in his “Elements.”