Four weeks after hatching the tail has practically disappeared, while appreciable quantities of yolk still remain. The young frogs are recognisable as specimens of L. archeyi very early by the presence of parotoid glands.

The eggs are laid beneath logs or in rotting stumps (Plate 59, Fig. 2), often surrounded by a moisture-conserving mixture of decaying wood, leaf mould and soil. They are always protected from light.

Archey (1922) recorded several instances of a frog sitting over a cluster of eggs, but owing to an accident to his specimens he was unable to decide the sex of the animals in question. The authors have since found several frogs crouching over egg clusters on Mt. Moehau, and proved these in each case to be males.

As amplexus has not been recorded for any species of Leiopelma it is not yet known whether fertilisation is internal or external. Ascaphus truei has internal fertilisation, but in this genus the male has a unique and specialised intromittent organ. On the other hand, Nectophrynoides, an ovoviviparous African toad (Noble, 1931, 15) achieves internal fertilisation without the aid of special copulatory organs. The presence of a male Leiopelma archeyi in association with a group of eggs (usually a cluster not far advanced in development) may possibly be an example of the so-called “brooding” habit shown by a few amphibians (Noble, 1931, 413), or it may have the function of ensuring external fertilisation. Possible support to the latter view is given by the fact that not all the eggs in a cluster are usually at quite the same stage of development, and that infertile eggs are fairly common. Yet another alternative is that the adult frog may provide moisture for the egg by means of urinary excretion, as may possibly be the case with the Australian toad Chiroleptes platycephalus (Needham, 1942).

The eggs appear to be long in maturing, for well-developed ova have been found in an ovary even in the winter. It seems probable, from the examination of a very limited number of specimens, and from artificially induced ovulation, that each female lays at least two clusters of eggs each season, one from each ovary.

The oviducts have wide anterior funnels and enlarge posteriorly into thinner-walled regions which may be regarded as ovisacs. These unite together in the middle line to form a median “uterus” which opens into the cloaca. A similar structure is found in Bufo, Alytes and Nectophrynoides (Noble, 1931, 273). Vestigial Müllerian ducts are invariably present in the males, uniting together anteriorly to the cloaca in the same way as the oviducts of the females.

As has been mentioned above, E. M. Stephenson made sveeral attempts to induce egg-laying in L. archeyi and L. hochstetteri. A few specimens were on several occasions injected with a gonadotrophic hormone preparation, Pregnyl, which in certain other anurans—e.g., Xenopus, readily induces ovulation and pairing. In spite of varied dosage, this treatment had no apparent effect on any of the specimens of Leiopelma involved.

In 1948, small quantities of fresh anterior pituitary from female specimens of Rana temporaria, crushed in 1/10th Holtfreter solution (modification of method of Hamburger, 1942, 32) were injected into three specimens of L. archeyi and one specimen of L. hochstetteri. Implantation of fresh anterior pituitary substance had previously induced egg-laying and amplexus in Ascaphus (Noble & Putnam, 1931). Five days later, one female specimen of L. archeyi thus treated laid a cluster of five eggs (Plate 59, Fig. 3), followed by a further two eggs a week later. A second female of the same species which had been injected at the same time as the first, laid two eggs a month after injection and a single egg a few days later. The third specimen of L. archeyi was a male, and showed no reaction to the injection. The eggs were all infertile.

Mr. S. Gittos' discovery (Turbott, 1949, 374) of the eggs of L. hochstetteri, and further description of these by Turbott (1949, 375) and N. G. Stephenson.