The influence of the position of the cut upon regeneration in Gunda ulvæ.

In 1899 Hallez (4) made the generalisation that the most important difference between the regeneration in Triclad and Polyclad Planarians was to be found in the fact that fragments of the former could regenerate in the absence of the central nervous system, whilst in the latter some portion of the cerebral ganglia must be present in order for regeneration to take place. Child (1) has confirmed the fact that the presence of cerebral ganglia, or at least intact nerve roots, is necessary for regeneration of the anterior end and sense organs of Polyclads. The experimental work by the same and other authors has also established that, among Triclads, the genus Planaria is able to regenerate completely in the absence of cerebral ganglia. The following notes, however, show that in another Triclad genus, namely, Gunda , anterior regeneration is, as in Polyclads, dependent on the presence of the central nervous system. The experiments described below were carried out in the Plymouth Laboratory of the Marine Biological Association during the spring of 1913. I am greatly indebted to the director and staff of the laboratory for constant kindness during the course of my work at Plymouth. I also stand under obligations to the Royal Society, the Zoological Society, and the University of Cambridge for the use of their tables at the Plymouth Laboratory.