WERNER MARCHAND 9 



During the period just mentioned the microscopic study of lower 

 organisms had made continuous progress and the anatomical investi- 

 gators soon began to discover favorable objects of research in the 

 histology of insects. The study of sense organs of lower animals had 

 since Johannes Miiller become a favorable subject of research. On 

 the other hand, the native fresh water fauna furnished the most varied 

 and suitable objects for microscopic study, and this fact led to re- 

 peated observations on tabanid larvae from the point of view of general 

 zoology, the determination of the species at hand being omitted with 

 an almost disconcerting regularity. We have, however, noted that 

 tabanid early stages were observed, by Scholtz in Breslau in 1848, and 

 even the species was identified, as adults had hatched from the pupae 

 collected. In 1878 Graber, in Czernowitz, Austria, in his studies on 

 the sense organs of insects, discovered a peculiar otocyst-like organ 

 in a Tabanus larva, called Graber's organ by later authors, a dis- 

 covery which he connected with that of similar organs in the larva 

 of Ptychoptera by the zoologist Grobben. His paper called forth an 

 article by Krauss in 1879, a pupil of Brauer in Vienna, according to 

 whom this organ had already been demonstrated by Brauer in the 

 tabanid larva in his zoological course. Krauss also declared the larva 

 defined by Graber as a fly-maggot to be a Tabanus larva, and to belong 

 to Tabanus autumnalis. Whether the species was really this or a 

 similar one, no one can say at present. However, to Graber belongs 

 the credit of the independent discovery of this organ and its minute 

 description. In a later work (1882) on the chordotonal organs of 

 insects, Graber figured another tabanid larva with many anatomical 

 details, demonstrating in it the chordotonal organs which had been 

 discovered by Leydig in Corethra plumicornis. These discoveries, 

 especially the otocyst-like organ, gave rise to scientific controversy, 

 Lecaillon in France (1905 and 1906) assuming that the organ must 

 in reality be a gland, while Paoli (1907) in an extensive work under- 

 takes to prove that it is not an auditory, but a sound-producing organ. 

 At the same time Paoli advanced an interesting theory about the 

 manner in which the organ is developed, though without reference to 

 phylogeny. 



With Lecaillon and Paoli an influence of economic entomology, 

 especially of agriculture, is notable in stimulating research, unques- 



