450 J. T. WILSON AND J. P. HILL. 
MatveritaAL AnD Meruops. 
For the purposes of our research we have had at our com- 
mand fourteen different stages of Perameles young. Among 
these stages P. obesula was represented by three specimens, 
while the remainder of the material was furnished by P. 
nasuta. 
The youngest was an intra-uterine specimen of P. obesula, 
rand from this early condition onwards we possess a pretty 
complete series of stages. 
The material representative of the more important stages 
has been sufficiently abundant to enable us to obtain complete 
series of sections in different planes. 
Decalcification was effected chiefly by means of nitric 
alcohol ; sections were cut in paraffin except in a few cases 
where celloidin was preferred. The stains used were Gre- 
nacher’s borax-carmine, hematoxylin, hematoxylin and eosin, 
hematoxylin and picric acid; the hematoxylin stains were 
chiefly used, and are greatly to be preferred, especially the 
double stains named. We find a very dilute solution (very 
faintly claret-coloured) of Renaut’s hzmatoxylic glycerine to 
give the best results. The stain should be light if to be fol- 
lowed by eosin, and deep (i.e. of considerably longer duration) 
if to be followed by picric acid. The latter (as also the eosin) 
is used in a weak solution in 90 per cent. alcohol. Sections 
were generally stained on the slide, being fixed by Mayer’s, 
or latterly by Maun’s albumen method. 
1 Owing to the enormous number of serial slides we had to work with, each 
slide containing very numerous sections, it was rather important to have a 
short and convenient method of designating any particular section in our 
notes and descriptions. We have found it exceedingly useful to employ a 
18 
~ 6-IN=E' 
number of the section in any given row, counting from the left-hand end. 
The Arabic numeral below the line refers to the number of the particular row 
of sections on the slide, counting from the top. The Roman numeral indi- 
cates the number of the slide in the series ; and the capital letter specifies 
the series itself. For ordinary work the last may often be omitted. The 
formula thus: Here the figure above the line indicates the 
