Videnskabelige meddelelser

Videnskabelige meddelelser


nections are most developed in the proximal part of the lamellae.

Towards the arch the lamellae are connected distally, and no bridges

are found proximally. Ossifications and teeth are found on both

sides, the most perfect on the outer side (Plate XIX). On the

inner side they are only to be found around the pores as disks,

each with a group of pointed hollow teeth, which just as many

genuine teeth may easiiy be loosened from their foundation.

Liitken^) compares Acanthocybium and the swordfishes and

uses the common features of structure as a proof of relationship

and maintains that the swordfishes are belonging to the scomberoids.

Jordan & Evermann^) write concerning Histiophoridæ

„Gills reticulated as in Xiphias, — — — the group represents a

younger stage in the development of Xiphias and is intermediate

between the latter and the scomberoid stock, from which both are

derived. The gabs are wide in the series Scomberomorus, Acan-

thocybium, Istiophorus, Telrapturus, Xiphias, but the natural

sequense seems evident."

Through the observation of these gill-types some questions arise.

Are the tooth-like formations in Acanthocybium and swordfishes

teeth? Although the enamel-tips are not distinct I shall

not hesitate to call the formations teeth. Indeed, it is

very Strange to find teeth on the gills of a fish ! 1 however think

that the layer of teeth-carrying ossifications of the gill-arch has

been continued out upon the edge of the branchial lamellae.

Next, of what use may it be to the fish that the gills are sup-

ported in this peculiar way? It is evident that the Xiphias-g\\\

must be less fit for water-respiration than ordinarily developed fish-

gills, for the water has to pass the pores in order to reach the

lamellae, the seat of the respiration, access being much easier

when the lamellae are not connected with each other.

Only parts of the above remarks are new, but the matter seemed

to me so interesting that I should like some attention to be turned

to them. If therefore other zoologists would deign to give their

opinion, these lines would have fulfilled their intention.


More magazines by this user
Similar magazines