6 PEOF. G. B. HOWES AND ME. H. H. 8W1NNEJJTON 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 x , 

 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 and 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. 



1 Of. Newman (Taylor tit.), 77, p. 222. 



