No. 4-] THE EYE OF SCUTIGERA FORCEPS. 207 



ences between them, Adensamer suggests calling the eye of 

 Scutigera a "pseudo-facet" eye. Rosenstadt ('96) discusses 

 the question as to whether the eye of Scutigera can be regarded 

 as a true facet eye, reviewing the arguments of Grenacher and 

 Adensamer. He also suggests a way by which an eye, as that 

 of Scutigera, could be developed from a true facet eye. 



The following work was done in the Biological Laboratory 

 of Bryn Mawr College, under the direction of Prof. T. H. Mor- 

 gan, to whom I am greatly indebted for valuable suggestions 

 and criticism. 



The species studied was Scutigera (Cermatia) forceps. 



For sectioning, the best results were obtained by hardening 

 the fresh material in corrosive acetic for fifteen minutes, then 

 running it up through the successive grades of alcohol. 



The dense pigment obscured all details, therefore a depig- 

 menting agent, as KOH, was used (cf. Parker, "The Eyes in 

 Scorpions," '87). The preparations were stained with iron- 

 haematoxylin. 



As a maceration fluid, a modification 1 of Bela Haller's fluid 

 was used. Material left in it for a year gave excellent results. 

 The separate ommatidia fell apart, and by gently tapping the 

 preparation the individual cells of each ommatidium could be 







isolated. 



By this means I have been able to make out more definitely 

 the structure of the different component cells than have the 

 authors mentioned above, and in some respects have been able 

 to add some points to their results. 



The eye of Scutigera forceps is nearly triangular in shape. 

 The corneal hypodermis is faceted, one ommatidium correspond- 

 ing to each facet. Each eye is composed of a^bout two hundred 

 individual units or ommatidia. 



Fig. i A shows 2 a single ommatidium, its proximal end 

 bordering on the inner cuticula or basal membrane. 



1 Bela Haller's mixture modified : two parts glacial acetic acid ; two parts 

 water ; one part glycerine. 



- The figures are all camera drawings: Fig. i A and B were drawn with a 

 No. 7 objective; Fig. i C and D were drawn with an oil immersion -j-V ; Fig. 2 A. 

 Z>, C, D, E, /'were drawn with an oil immersion T V- 



