LATERAL AND CENTRAL EYES OF SCORPIO AND LIMULUS. 181 



The lateral eyes of Limulus required special treatment, 

 on account of the density and extent of the chitinous lens- 

 area. The vertical sections in this case were cut with the 

 hand, and were more difficult to obtain in satisfactory condition 

 than any of the others. 



Drawings. — The figures which illustrate this memoir are 

 not drawn to a constant scale. With a few exceptions, they 

 are not representations of actual sections, but combination- 

 drawings, intended to place before the reader results, and not 

 the crude material from which the results are derived. The 

 colouring of the drawings is purely conventional. In most 

 cases the eye-pigment forms, on solution by the nitric acid, a 

 fine madder-brown tint, which stains the nuclei, and often the 

 protoplasm, of the cells of an entire section. The pigment 

 thus becomes diffused as soon as the attempt is made to remove 

 it. Pigment granules in process of solution appear of a deep 

 red-brown colour ; when not acted on at all they are absolutely 

 black, or, in some cases, greenish grey. 



The Lateral Eyes of Scorpions. 



Of Androctonus funestus, Ehr. — The lateral eyes of 

 Scorpions are placed on the margin of the prosomatic shield, 

 in a group on each side anteriorly. The number of separate 

 lenses developed differs in various sub-genera, each lens indi- 

 cating a separate eye. In Androctonus the eyes are more 

 numerous than in other Scorpions, each lateral group showing 

 in A. funestus as many as five lenses, three larger and two 

 smaller. The smaller lenses are equally entitled to count as 

 eyes with the larger. It is, however, difficult without great 

 care and minute examination to distinguish mere tubercles of the 

 chitinous integument from eye-lenses. ^This is, of course, 

 readily done either when sections are cut, or when the sub- 

 jacent tissues are cleaned away from the ocular area of the 

 chitinous shield, and the tubercles and lenses are examined by 

 transmitted light. 



