184 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
ralists under the name of cells. Cells are found only in living bodies j 
and it is very probable, though by no means certain, that no life exists 
outside of cells, or in any other bodies. For this reason, to determine 
the essential powers and peculiarities of cells, and to discover the modi- 
fications they undergo, is the fundamental problem of zoology and botany 
at present. Indeed, biology might almost be defined as the science of 
cells. 
Since, however, microscopic anatomy, which is that branch of science 
which deals especially with the forms and appearance of cells, has been 
more actively prosecuted by medical men than by zoologists, our knowl- 
edge of the tissues of the higher vertebrates is much more complete than 
of the lower animals. Of the histological structure of insects singu- 
larly little is known, although they are particularly favorable objects for 
microscopic investigation. The most extensive series of observations 
are those of Leydig, which are summarized in part in his invaluable 
Lehrbuch der Histologic, published in 18.38, and in part in shorter special 
papers scattered through various scientific journals of the last twenty 
years. Max Schultze has made several important contributions, and 
there are besides a few excellent single papers, by various authors, 
notably Dr. Von Basch, Landois, Claparede, Graber, O. Schmidt, &c. 
Several of Professor Rudolph Leuckart's pupils have made very valuable 
additions to our knowledge of insect histology. The writings of earlier 
naturalists contain many observations of importance, but the ground 
covered by them must now be gone over again and viewed from the 
stand point of modern anatomy. 
When I began the work the results of which are here described in 
detail, 223 1 found that very few histological observations had been made 
on the grasshoppers, or, indeed, on other insects. I feel that this is very 
unfortunate, because it prevents my judging of the accuracy of my own 
observations by comparing them with the results obtained by others. I 
must therefore anticipate that some at least of my conclusions will here- 
after require modification. 
I regret very much the incompleteness of this report, occasioned in 
large part by my inability to devote myself longer than a little over five 
months to the work. My results are derived chiefly from the study of 
the locust, 224 to which I have added a limited number of observations on 
Anabrus purpurascens. I have endeavored to increase the value of the 
article by incorporating a considerable number of bibliographical refer- 
ences. I hope that with these additions this report wdl assist other 
American students in becoming acquainted with the present state of 
our knowledge of the histology of insects without having to search far 
and wide for the authorities. In brief, I attempt to give a bibliographical 
index to the general outline of the subject, and to describe in detail such 
523 A preliminary report has been published in the First Annual Report of the Commission, pp. 273- 
277. 
534 The observations are mostly made of the Caloptcnus femur-rubrum, the common red-legged locust, 
and on QCdipoda sordida. 
