MAYER: DEVELOPMENT OF WING SCALES. 299 
for constant kindness, valuable advice, and criticism in reading over 
the proofs. Mr. Samuel Henshaw obtained for me the pupie of Va- 
nessa antiopa, from which it was shown that the scales arise from 
hypodermis cells. I am also indebted to him for many other acts 
of kindness. I also wish to thank Mr. George Oenslager for the analysis 
of the mineral bases of the hemolymph, and Professor George L. Goodale 
for allowing me the use of the spectroscope apparatus of the Botanical 
Laboratory. 
HARVARD UNIVERSITY, February, 1896. 
Norn. — The statement on page 231, which includes Schäffer among 
those who had inferred that the scales are the product of modified hypo- 
dermis cells, may seem to misrepresent that writer, for he states explieitly 
(89, p. 613) that the scales are evaginations of greatly enlarged hypodermis 
cells: “ Beide Gebilde [scales and hairs] sind, allgemein gesagt, Ausstiil- 
pungen von sich stark vergrösserenden Hypodermiszellen. Die allerdings 
selbstverstiindliche, aber bisher nicht beobachtete Abstammung der Schup- 
penmutterzellen von der Flügelhypodermis konnte ich sicher constatiren.” 
Since Mr. Mayer’s absence from Cambridge makes ib impossible for him 
to revise the proof of his paper, I take the responsibility of explaining that 
Schiiffer’s conclusion, though hardly to be called purely a matter of inference, 
rests upon much less satisfactory and complete evidence (he figures only one 
stage in the development of the scales) than that furnished by Mr. Mayer. 
E. L. Mark. 
May, 1896. 
