478 SHAFER 



Moreover, it would be of as much advantage to increase the 

 sensitive receiving surface (rhabdome surface) in the eye used 

 in dim light as to increase the dioptric or light gathering sur- 

 face. The complicated rhabdome surface of the turban eye of 

 Callibcetts shows this increased sensitive surface and further- 

 more, the retinulae of the " abkonical ring " each have well de- 

 veloped rhabdomes. The rhabdomes of the larger ommatidia of 

 all the divided eyes are larger than those of the small ommatidia. 



Stanford University, 

 April 28, 1906. 



LITERATURE CITED. 



Exner, S. 



1891 Die Physiologie der Facettirten Augen von Krebsen und Insecten. 

 Leipzig u. Weine 

 Grenadier 



1879 Untersuchungen iiber das Sehorgan der Arthropoden, Insbesondere der 

 Spinnen, Insecten und Crustacean. Gottingen. 



Zimmer, C. 



1897 Die Facetten Augen der Ephemeriden Zeit. f. Wiss. Zool.. Bd. LXIII, 

 pp. 236-262. 



Kellogg, V. L. 



1898 The Divided Eyes of Arthropods. Zoolog. Anzeig., Vol. 21, pp. 280- 

 281. 



1900 Notes on the Structure and Life-history of Blepharocera capitata Loew. 



Ent. News, Vol. II, pp. 305-318. 

 1903 Net Winged Midges of North America (Blepharoceridse). Proceedings 

 Cal. Association of Science, 3 series, Zool., Vol. Ill, No. 6. 

 Pictet 



1843 Histoire naturelle des Insects NeVropteres. Famille des Ephemerines. 

 Geneve, 1845. 

 Eaton 



1888 Monograph of recent Ephemeridae or Mayflies. Trans. Linn. Soc. 

 London, 2 series, Vol. Ill, Zool. 

 Carriere, J. 



1893 Kurze Mittheilungen aus Fortgesetzten Untersuchungen liber die Se- 

 horgen. Zool,, Anz. IX. 

 Ciaccio, G. V. 



1880 Sopra la Notomia Minuta Degli Occhi Delia Cloe diptera. Reviewed in 

 Journal of the Royal Mic. Soc, 1882, II, p. 609. 



EXPLANATION OF FIGURES. 



The sections from which the following drawings and microphotographs 

 were made were cut 3 to 6 microns in thickness. They were stained either 

 with Haedenheim's iron hematoxylin or by a modified Weigert's hematoxylin 

 method. Some sections were cross-stained with good results by safranin in 



