Abstract Before leaving New Zealand in 1901, in order to return to England after an absence of fourteen years in Australasia, I took special care to preserve material for the investigation, by modern methods, of the minute histological structure of the pineal eye of the native Lamprey (Geotria australis) and of the Tuatara (Sphenodon punctatus). Three years ago I published the results of my investigations on Geotria (Dendy, 1907, a), for which the material I had obtained proved amply sufficient. In the case of Sphenodon, however, I had been able to preserve the brain and pineal eye of only a single adult specimen. The pineal eye was detached from the brain and preserved separately, together with the surrounding portion of the cranial roof. This I kept in my own possession, but the brain was given to Prof. Howes for transmission to Prof. Elliot Smith. My investigations have been greatly delayed by various unavoidable circumstances, and especially by the pressure of other engagements. My professional duties called me to South Africa in 1903, and it was not until I had fairly settled down in the newly created chair of Zoology at Cape Town, and had imported from England the necessary apparatus, that I found an opportunity of preparing sections of my Sphenodon material. These sections were not fully examined until after my return to England once more in 1905.