6 PROF. G. B. HOWES AND MR. H. H. SWINNERTON ON THE 
In the foregoing list the stages and numbers are those of Dendy’s series, described 
in the Quart. Journ. Microsc, Sci. vol. xlii. p.10. Those marked * were found requisite 
as our investigation advanced, and were very kindly supplied by him at our request, 
and those marked f were incubated in our own Laboratory from unhatched eggs. The 
latter, six in number, packed close in moist sand in a 1-lb. canister with a perforated lid, 
were brought over by Mrs. Dendy and kept during the voyage from New Zealand in her 
cabin. One only decomposed, and of the five which remained, three ran the full deve- 
lopmental period, the enclosed young making good their own escape. These lived from 
three to four months, and for their reception we have added to Dendy’s series a Stage T. 
At this stage the coloration is the same as at S, but as an advance upon that there is 
a complete absence of all traces of the yolk-sac and shell-breaker, and the appearance 
in the thoraco-lumbar region of the all characteristic median dorsal languets (spines, 
auct.), such as are already present at Stage S in the so-called ‘‘ nuchal” and the caudal 
tracts. ‘These appendages, whose existence is expressed in the native name Tuatara !, 
are liable to no slight individual variation. Three tracts are present in the adult, viz. 
“nuchal,” thoraco-lumbar (‘ dorsal”), and caudal, as recognized by Boulenger in his, 
the latest, diagnosis (89. p. 2), with consequent scapular aud sacral intervals. Buller 
(76. p. 324) and Newman (77. p. 230) have called attention to the existence in the 
region of the cervical space of a conspicuous pigment-patch; and, concerning the 
numerical variation of the “spines” in the adult, they give for the ‘nuchal ” series 
10-14, for the thoraco-lumbar 15-20. From examination of eleven specimens present 
in our own collection and that of the British Museum of Natural History, we find the 
extremes range from 6 to 14 for the “ nuchal” and 15 to 24 for the thoraco-lumbar 
series. In two specimens of our Stage 'T they number 10 and 18 respectively. 
With a view to ascertaining the limits of individual variation, and thereby 
rendering the present memoir as complete as possible anatomically, we have examined 
all the dried skeletons within our reach—viz., the complete skeletons of nine adults, 
fragments of some six to eight others, and the complete skeleton of a half-grown 
individual in the possession of the Royal College of Science, Dublin. For the 
privilege of examining all but two, which are at South Kensington, we are 
indebted to Prof. A. C. Haddon, F.R.S., to Prof. C. Stewart, F.R.S., of the Royal 
College of Surgeons Museum, to Dr. R. F. Scharff, Keeper of the Natural History 
Department of the Science and Art Museum at Dublin, and to our friends in the 
British Museum of Natural History. 
Beyond this, we have had recourse where necessary to dissection of six spirit- 
specimens in the Teaching Collection of the Royal College of Science, two of which 
were presented by Prof. Dendy in the spring of 1899, 
