a | 
DEVELOPMENT OF THE SKELETON OF THE TUATARA. 
3. MeEtTHoDsS AND RECONSTRUCTION. 
Methods.—Dissection was resorted to only in the later stages, and wherever the 
elements under consideration were fully formed. Throughout the earlier stages, and 
in the later where necessary, microscopic sections were relied upon; and further, as 
for example at Stage S and in dealing with the carpus and tarsus, dissection was duly 
checked by section, as a means of ensuring accuracy of detail. 
The microscopic sections were in all cases mounted serially, the plane of section 
being determined by the object in view (as set forth in the accompanying description 
of the Plates). After preliminary experiment with the Green Lizard (Lacerta viridis), 
it was found that differentiation of the skeletogenous tissues could best be obtained 
by staining in bulk with Ehrlich’s hematoxylin, and afterwards on the slide with 
Griibler’s orange G. For this suggestion and much subsequent aid we are indebted 
to Mr. M. F. Woodward, Demonstrator of Zoology, Royal College of Science, London, 
than whom no better manipulator or master of micro-chemical technique exists ; and 
we found, as our work proceeded, that much time is to be saved by dissolving the 
orange in 70 p.c. alcohol, with the addition of a few drops of glacial acetic acid, 
thus eliminating the tedium arising out of the use of a mere aqueous solution. ‘The 
results of this method are exceedingly satisfactory, cartilage being as a rule differen- 
tiated blue, bone in all its forms deep yellow, while the other tissues behave each in 
its own way. 
Reconstruction—Since the time has now arrived at which mere dissection is 
insufficient for the study of the facts of skeletogenesis, recourse was had to the 
so-called Bornean method of reconstruction from microscopic sections!. We were 
under the necessity of working with thin plates, and found that if made of the 
Bornean mixture of beeswax and turpentine there was difficulty in preparation and 
lability to snap. By substituting vaseline for turpentine, we entirely overcame all 
this, and we can confidently recommend our mixture as reliable. 
The figures which constitute Pl. III. and figs. 7 and 10 of Pl. VI. are all from 
models prepared from plates thus made. For the most part the sections of the animal 
were cut to a uniform thickness of 10 «, and each plate made to that of 1 millim. 
Tracings were then drawn upon the plates, by means of the camera lucida, of sections 
at regular intervals, determined by the degree of magnification (every fourth section 
for a magnification of 25, every third for that of 33, and so on). In cutting out the 
tracings, trabecule were left where necessary for holding the parts together during 
reconstruction, and afterwards cut away. For the process of cutting, the best results 
were obtained by the use of a needle, the plates being laid upon glass. 
* Earlier achievement in the same direction must not be overlooked. In England it stands memorably 
associated with the Huxleyean traditions: ef. E. T, Newton, ‘‘ On a New Method of Preparing a Dissected Model 
of an Insect’s Brain from Microscopic Sections,’ Journ. Quekett Microscop. Club (I.), vol. vy. 1878, p. 150, and 
Qu. Journ. Micr. Sci. (n. 8.) vol. xix. p. 340. 
