2 I 2 HEMENWA Y. [VOL. I. 



early in their existence, thus proving their cell nature. He 

 also states that in an adult these can be vaguely seen. In no 

 eye did I see an indication of nuclei in the segments of the 

 crystalline body. 



Cross-sections show the segments to be arranged in no reg- 

 ular manner. In a complete series of cross-sections one omma- 

 tidium was followed, and camera drawings at the high and low 

 level were made of each section. 



It was thus possible to trace each segment and find the 

 number of segments and their relative position. In most 

 ommatidia the number counted was ten to eleven, but in one 

 ommatidium I was able to trace twelve. It must be under- 

 stood that in a single section no more than six to eight appear. 

 This can be seen by referring to Fig. 2. 



SUMMARY. 



The species described by Grenacher is Scutigera (Cermatia 

 araneoidea) ; by Adensamer, Scutigera coleoptrata ; by myself, 

 Cermatia forceps. 



The latter is the only American Scutigera. 



The differences in the accounts are probably to be explained 

 in part by the fact that the individuals studied were of different 

 species. 



(1) The number of ommatidia in each eye of Scutigera for- 

 ceps is about two hundred. In Cermatia araneoidea (Grenacher) 

 the number is given as one hundred. 



(2) The crystalline body was found to be made up of ten 

 to twelve segments, instead of six to nine. No nuclei were 

 observed in these segments. 



Each ommatidium is made up of the following cells : 



(3) Elongated pigment cells surrounding each ommatidium, 

 sixteen to eighteen in number (/, Fig. I A). 



(4) An outer tier of pigment cells, embracing the distal 

 portion of the crystalline cone, ten to twelve in number (/i, Fig. 

 i A). 



(5) A middle tier of cells of ten to twelve (/ 2 , Fig. i A). 



(6) An inner tier of cells situated at the proximal end of the 



