( ll) 
members of the series” (Bateson, “ Materials for the Study of 
Variation,” London, 1894, p. 84). This type of abnormality 
is of rare occurrence ; Mr. Bateson is only able to quote four 
examples of it amongst the Insecta, and two of these are 
doubtfully genuine. The undoubted cases are Cimbex axillaris 
and Bombus variabilis, both insects having the left antenna 
partially developed as a foot (Zc. pp. 146-148). I daresay 
that other cases of homeosis amongst insects have been 
recorded during the past twelve years, but if so, I have not 
XXxiv ] 
come across any accounts of them. The abnormality now to 
be described seems to be of the nature of a homeeotic variation. 
When dissecting a cockroach of the genus Panesthia, apparently 
a new species allied to P. sinwata, Sauss., I observed that the 
right maxilla was replaced by a hard chitinous structure 
superficially resembling a mandible; the left maxilla and 
both mandibles were perfectly normal. On removing and 
closely examining the right ‘“‘ maxilla” it was seen to bea 
densely chitinised and rugose organ, roughly approximating 
in shape and size to a normal mandible. This ‘‘maxilla” at 
the base is large, but it tapers distally and the apex bears a 
small finger-like process. Traces of segmentation are seen in 
two circular grooves and in the different size of the parts 
defined by these grooves; the organ may be regarded as made 
up of four segments, the terminal small process being one, 
but it is perfectly rigid and the segmentation is only visible 
on close examination. The basal segment is hollowed out on 
its inner face and it is this feature which increases the general 
resemblance of the structure toa mandible. Without going 
so far as to say that the abnormal “maxilla” of the cockroach 
under notice reproduces the ancestral condition of a mandible, 
attention may be drawn to the view that the mandibles are 
derived from a four-segmented organ, advocated by Wood- 
Mason and other entomologists. _Wood-Mason moreover has 
observed that the mandibles of the embryo of Panesthia 
javanica are segmented, and in the larve and adults of the 
same species he distinguished a groove across the back of the 
mandible at the base, representing in his opinion the remains 
of a joint. The cockroach exhibiting the variation described 
