332 PROCEEDINGS OF SOCIETIES. [^°oumL, Dec? riS? 
of certain Insects of tlie order Thysanura," the President called upon 
Mr. Mclntyre to read his communication before proceeding to the 
discussion. 
Mr. J. Beck said the view his late brother held as to the structure 
of the Podura scale was that the markings were caused by wedge- 
shaped elevations running from the quill to the apex of the scale. 
He had himself paid great attention to the scales of Thysanuradee, 
with a view to ascertain their structure. He hoped that microscopists 
would discontinue the use of the name " Podura " scale, as it involved 
great confusion, the apparent structure of the scales of diJBferent 
genera in them not being the same ; and he hoped in speaking of the 
genera from which test-objects are taken that the scientific name of 
Lepidocyrtus curvicollis would be adopted. He thought that in order 
to ascertain the structure of the scales of this family, especially of 
those species possessing delicate scales, the structure of all must 
be taken into account, and assuming that the structure of all was 
similar in plan, determine whether the individual appearance was con- 
sistent with this idea. In Lepisma saccharina the appearance was 
undoubtedly due to corrugations on the one side running from the 
spine to the apex ; to corrugations on the other side radiating from 
the spine to the circumference ; this structure producing the appear- 
ance so familiar to observers. The correctness of this idea of the 
structure could be easily tested by running moisture on either side, 
as explained in his brother's work on the microscope. In Petrobus 
maritimus there was, as might be proved by experiment, the same 
structure with but slight varia-tion, and the same might be said of 
Macrotoma, of which Mr. Mclntyre had spoken. To ascertain whether 
the appearances in Lepidocyrtus curvicollis were consistent with the 
existence of lines, he had examined many butterfly scales having cor- 
rugations, and selecting those of the Peacock butterfly as the most 
suitable, found that where the scales overlapped one another at about 
an angle of 30° the lines were obliterated, and the " notes of exclama- 
tion " appeared. To resolve this object he considered almost as good 
a test as L. curvicollis. He thought there was prima facie evidence 
that appearance on the test-scale was due to a like cause ; but he had 
reason to modify his opinion, for observation had shown that the 
structure of the two sides of the scale was different. If a piece of 
glass be laid on the insect, the scales adhering would have their under- 
side uppermost, and if breathed upon while under the microscope, 
moisture would be seen to run up and down along corrugations, as in 
L. saccharina or Petrobus ; but if this experiment be tried on the upper 
side of the scale the moisture would spread over the surface, and 
present the appearance of an undulating membrane. He inferred 
from this that the structure of Lepidocyrtus scale was similar to that 
of other genera in this group, slightly varying in the corrugated and 
undulating appearances ; but still that in Lepidocyrtus as in Lepisma, 
the true structure on the under-side of scale is a series of corruga- 
tions on one side, and ttat the other side was slightly undulating, or 
nearly smooth ; and that the " notes of exclamation " were due 
entirely to the refraction of light. This idea was confirmed by the 
appearance of the scale when the object-glass was out of focus. 
