II - On the nervous system of the starfish Mathasterias glacialis (L.)

Abstract

In the year 1815, Tiedemann observed on the oral surface of the disk of the starfish Astropecten aurantiacus (L) a circumoral band of tissue continuous, in the mid-line of each arm, with a radial band. To these bands he ascribed a vascular function. Johannes Müller (1850), however, indicated that the radial and circular bands were more properly to be regarded as nerve cords, an observation which Owsjannikow (1871), Greeff (1871, 1872, a , 1872, b ), Hoffmann (1872), and Teuscher (1876) subsequently confirmed. Lange (1876), while not accepting the findings of previous authors as to the nervous nature of the circumoral and radial cords, discovered two ridges of tissue above each of the “V’’-shaped radial cords, one lying to the right and the other to the left of the mid-line. These are constituted by thickenings of the coelomic epithelium which lines the radial perihaemal canals, and were considered by Lange to represent nervous tissue. This opinion has been substantiated by Ludwig (1878), Hamann (1883, 1885), and Cuénot (1891) among others; but these and all recent investigators agree that the radial and circumoral cords must also be regarded as constituting part of the asteroid nervous system. Cuénot (1891) therefore distinguishes between the part of the nervous system derived from the ectoderm, such as the circumoral and radial cords, and the part—presumably of mesodermal origin—situated in the coelomic epithelium.