192 PROFESSOR E. RIY LANKBSTER AND A. G. BOURNE. 



1 I central eyes of the Scorpions there are no interneural cells of 

 ectodermal origin, as there are in the lateral eyes, and that 

 their place is taken by intrusive connective tissue. In any 

 "case it is by this name that we shall designate a largely de- 

 veloped pigmentiferous framework, which pervades the hinder 

 chamber of the ommateal capsule, and has not hitherto been 

 described in any similar eye. 



In fig. 8 (as also in fig. T), for the sake of clearness in other 

 details, a large part of the pigmentiferous intracapsular connec- 

 tive tissue has been omitted. But a series of epithelium-like 

 cells (/>) and a group of cells resembling adenoid tissue (r) has 

 been retained in the drawing. All these cells possess before the 

 de-pigmenting process abundant black pigment granules in 

 their protoplasm. 



The layer of cells {p) closely adheres to the inner wall of the 

 ommateal capsule, and when the pigment is present gives a 

 deep black limiting border to the capsule, as shown in fig. 9. 

 The cells are again seen in the partially de-pigmented prepa- 

 ration drawn in fig. 10. They may be called the " intracapsular 

 pavement.'^ At the periphery of the capsule these cells become 

 continuous with a series of very delicate pigmentiferous 

 cells, which lie close beneath the capsular septum (w), between 

 the anterior extremities of the nerve-end cells. These are seen 

 as flakes of pigment in fig. 9 5, more clearly in fig. 10 5, and 

 diagrammatically in fig. 11 s and fig. 14 s. They may be known 

 as the "anterior intra-retinular pigment cells." These cells 

 are exceedingly thin and delicate, and readily destroyed by the 

 acid which is used to remove the pigment. It is on this 

 account that they have escaped the observation of Grenacher, 

 whilst on the other hand Von Graber has seen their nuclei, and 

 attributed them not to interstitial cells, but to the nerve-end 

 cells themselves. These nuclei are undoubtedly the so-called 

 *' anterior nuclei" of Von Graber, which he has seen and 

 fi<Tured with especial clearness in the central eye of Bu thus. 



A very thin section of the ommateum of the central eye of 

 Androctonus, which has been but little or not at all acted upon 

 by acid, shows a second series of pigmentiferous cells similar 



