ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
519 
extremely local, but are generally confined almost to identical habitats, 
removed from which they do not long survive. Supposing the group to 
be a natural one, descended from a common ancestor, we are compelled 
to believe that such differences as appear among them are the results 
of accumulated variation, not greatly influenced by external selective 
causes. In this respect the Diplopoda offer a most striking contrast to 
the Hexapoda, and the results are in accordance. There are more 
millions of species of the latter than there are thousands of the former. 
In attempting to embody in the classification of the Diplopoda a recog- 
nition of certain structural differences found to be invariable, several 
natural and distinct groups of families have been recognised as orders. 
The author proposes now to divide the orders Diplocheta and Mero- 
cheta. From the former it is proposed to separate the true Iulidae and 
their allies under the name Zygoclieta, leaving under the Diplocheta 
Spirostreptoidea and Cambaloidea. The Merocheta will, in the restricted 
sense, contain numerous families allied to the Polydesmidae, with twenty 
closed rings. The new order Coelocheta will accommodate the Lysio- 
petaloidea and the Craspedosomatoidea. 
y. Protracheata. 
Peripatus.* — Mr. T. Steel has some very interesting remarks upon 
this creature, a number of specimens of which he has from time to time 
observed in New South Wales; in favourable summers such as that of 
1894—5 he observed no fewer than 579 adults in one district, but in the 
summer of 1895-6, which was preceded by a prolonged spell of very 
dry weather, Peripatus was very scarce. Dry conditions, such as these, 
and the attendant bush fires, must, Mr. Steel remarks, cause an enormous 
mortality among lowly land-dwelling creatures, and it is greatly to be 
desired that as much information about them as is possible should be 
gained, since many local forms are certain to be now rapidly approaching 
extermination. In a favourable summer the individual adults range 
much larger in size than in an unfavourable one ; the dry conditions 
appear to have stunted their growth. The author does not know what 
became of the large sized individuals of 1894-5, whether they perished 
or whether they shrunk in size. A very noticeable peculiarity is the 
intensely local nature of Peripatus ; considerable numbers would be met 
with in a very restricted area, and, without any apparent cause, none at 
all, or very few, would be found on precisely similar ground adjoining. 
After a little experience Mr. Steel got to know the likely-looking parts, 
and even the most promising logs uuder which to search. 
The colours of the individuals were exceedingly variable, 77J per 
cent, were black or blue-black, 6^ per cent, were black speckled with 
brown, 10 per cent, were brown but had black antennae, and 6 per cent, 
were entirely brown. When a number of specimens of the brown form 
are put in spirit together, the spirit has a distinct brown tinge, which 
would show that the colour-pigment is to some extent soluble in alcohol. 
The author is uncertain whether the species was originally brown or 
black. The adult females appear to be invariably larger than the males, 
and also a good deal stouter in proportion to their size. They do not 
Proc. Linn Soc*. N.S.W., xxi. (1896) pp. 91-103. 
