The morphology of the pineal region in teleosts / Robert J. Terry.

  • Terry, Robert J. (Robert James), 1871-1966.
Date:
[1910]
Catalogue details

Licence: In copyright

Credit: The morphology of the pineal region in teleosts / Robert J. Terry. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    ported by mesenchyma rich in blood-vessels. The latter, contin- uous with vascular channels in the vicinity of the epiphysis, post- velar arch and paraphysis, are close under the velar epithelium. No difference was observed in the thickness of the epithelial coat of the anterior and posterior aspects of the velum as has been de- scribed in Acanthias by Minot (’01) and in Acipenser by Kupffer (’06). Post-velar Arch (Fig. 2, PV). The name ^‘post-velar arch” was given by Minot (’01) to the curve in the brain roof which lies between the velum and the epiphyseal anlage. This is the part of the diencephalic roof called Zirbelpolster by Burckhardt and the region of the post-paraphysis of Sorensen (’94). Out of this region is developed in the ganoids and some of the bony fishes the evagination called by Goronowitsch (’88) the dorsal sac. In Ospanus, the arch does not expand into a sac, but on the contrary diminishes in extent and finally disappears. In the stage under discussion, the post-velar arch is a small dome-shaped evagination of the diencephalic roof extending sagittally between the superior commissure and velum and going over laterally into the intermedi- ate tubercles. At no time is the evagination so extensive as it is in Salmo where, as Hill (’94) states (p. 242) “it bears some resem- blance in form to the epiphysis.” The arch in Opsanus rises a little higher than the base of the epiphysis but not so high as the paraphyseal fold. Its simple cavity can be followed for- ward to the pedicle of the velum, on either side of which it becomes continuous with a short blind recess (fig. 6). In transverse sec- tions through the posterior part of the velum, these two small recesses appear as lacunae surrounded by the velar and ependymal epithelium. In structure the post-velar arch consists of a layer of rather thick ependyma. Anteriorly, this continues with slight increase in the height of its constituent cells into the velar epi- thelium. Posteriorly, it changes abruptly to a very thin layer at the level of the superior commissure. The latter lies upon the epithelium of the caudal part of the arch, over w'hich it extends in a lateral direction as far as the intermediate tubercles. Folds of the epithelium are not present, nor are there any diverticula such as Herrick (’91) has found in the walls of the dorsal sac of