190 LIVERPOOL BIOLOGICAL SOCIETY. 
List of Works referred to in Foregoing Paper. 
1. Weismann. Die Entwicklung der Dipteren. Leipzig, 
1864. 
2. Palmén. Zur Morphologie des 'Tracheensystems. 
Helsingfors, 1877. 
3. Kowalevsky. Hin Beitrag zur Kenntniss der Excretions- 
organe. Biolog. Centralblatt. Bd. IX. 1889. 
4. Raschke. Die Larve von Culex nemorosus. Berlin, 1887. 
5. A. M. Mayer. Researches in Acoustics. American 
Journal of Science and Arts, 1874. 
6. Grenacher. Untersuchungen tber das Sehorgan der 
Arthropoden. Gd6ttingen, 1879. 
7. Graber. Ueber den propulsatorischen Apparat der 
Insecten. Archiv fur mikroskopische Anatomie. 
IEG 1D 
NOTE. —The substance of the foregoing communication 
has been printed in the second volume of the “ Studies 
from the Biological Laboratories of the Owens College,” 
and has formed my inaugural dissertation for the Degree 
of Ph. D. in the University of Leipzig. For permission 
to reprint the plate I have to thank Professor Marshall, 
the editor of the ‘‘ Studies.” 
