The First Abdominal Segment of Embryo Insects. 
87 
ON THE APPENDAGES OF THE FIRST ABDOMINAL 
SEGMENT OF EMBRYO INSECTS. 
By WM. M. WHEELER. 
Much of what is contained in the following paper was presented to the 
Wisconsin Academy of Sciences, Arts and Letters at its annual meeting in 
December, 1888. Graber's summary [’88], embodying as it does all that 
was known of the curious organs on the basal abdominal segment of em¬ 
bryo insects up to 1888, would seem to render superfluous a second general 
contribution at so early a date. Nevertheless I have been led to undertake 
the task for several reasons: First, several brief articles have appeared 
since the publication of Grabev's comprehensive paper; secondly, I have 
myself made some observations which fill a few of the gaps neces¬ 
sarily left in the German investigator’s resume, and thirdly, as I take a 
very different standpoint in regard to the interpretation of the problematic 
appendages, I feel in duty bound to reproduce all the facts from which my 
conclusions are drawn. 
This paper does not purport to be a final monograph on the subject—- 
such a task can be undertaken only when the embryos of many more in¬ 
sects have been carefully studied — but a resume of facts and theories up 
to the close of 1889. After giving an account of my own investigations in 
the first part, I shall in the second portion pass to an account of the work, 
of other observers, and in the last part consider the theories which have 
been advanced in regard to the original function of the problematic organs. 
The descriptions of the organs in Blatta and Periplaneta and the whole of 
the theoretical portion are essentially the same as when presented to the 
Academy in December, 1888. 
For the sake of avoiding repea,ted circumlocution I shall call the appen¬ 
dages of the first abdominal segment pleuropodia — a name both sugges¬ 
tive of their origin from foot-like organs and their tendency, when 
fully developed, to take up a position on the pleural wall of the embryo. 
Should the theory advanced in the latter part of the paper prove to be cor¬ 
rect, I would suggest that the term adenopodium be substituted for 
pleuropodium. 
I shall not treat of the abortive and very transient appendages which 
appear on some or all of the abdominal segments, since the interested 
reader will find a complete resume of our fragmentary knowledge of these 
structures in Grctber's paper [’88]. Nor do I propose to enter into the con¬ 
troversy as to whether the ancestral insects were homopod or heteropod„. 
