ABSTRACT
The water-soluble carcinogenic hydrocarbon, 1 : 2 : 5 : 6-dibenzanthracene-α-β-endo-succinate, has been implanted in carefully graded doses into gastrulae of Triton alpestris.
An optimal dose for neural tube formation was found at 0·0125γ per embryo, and for palisade inductions at 0·000125γ per embryo.
It is suggested that the action of this hydrocarbon at least is direct, imitating the action of the naturally occurring organizer substance, and not indirect, by injuring the ventral ectoderm so as to liberate the masked organizer substance which it contains. The effective range of dosage resembles that of many biologically active substances.
A parallelism exists between the frequency and the size of the neural tube inductions.
It may be of interest that when the slides were kindly examined by Dr Glücksmann, pycnotic nuclei were not found to any greater extent at the higher dosages than at the lower ones. This again suggests that degeneration phenomena did not play a large part.
