()S mTLI.KTIN (IF TIIK 



they form a regular row through the whole length of the outer member 

 (Fig. 22, (•). They are mostly couiincd to the outer members, but in 

 some rods a single one of unusual distinctness is found in the inner 

 member. 



I now pass to the least developed and most degenerate eyes. Perhaps 

 the specimen most interesting in tliis respect is the one shown in 

 Figure U. In this the lens is entirely absent, a continuation of the 

 pigment layer of the retina extending without break entirely over the 

 space that this structure should occupy. The series of sections of this 

 eye is complete, and every section is as perfect as the one from which 

 Figure C) was drawn ; so there can be no possibility that the absence 

 of the Ions is due to artificial causes, or that an eiTor in observation 

 has been made. I should add, also, tliat I have an equally complete 

 series of sections of the other eye of the same individual, and this shows 

 the same structure in every particular. Over a portion of the outer 

 moiety, the pigment is disposed in a double layer (Fig. 7,ju</.' and /u;/."). 

 The outer of these layers is more directly continuous, both in thickness 

 and direction, with the pigment layer of the retina. The inner layer 

 presents a considerably thickened mass, i>iii.", irregularly lenticular in 

 form. From the appearance shown in this figure, one is tempted to 

 regard this pigment mass as a remnant of the Ions, the thinner portion 

 of the layer at its edges, which connects it with the ]ugment layer of the 

 retina, representing the iris. It is very doubtful, however, if such is 

 the case. "With such an interpretation the outer pigment layer {pig.') 

 woidd seem to represent the inner layer of the cornea ; and this would 

 atVord an explanation, not obvious otherwise, of the continuity of the 

 layer over the pupil. But there are several ditiiculties in the way of 

 these convenient interpretations. In the first place, the pigment mass 

 under consideration is found on examining the entire series of sections 

 to be very irregular in form, and, as shown in Figure 6, to become con- 

 fluent with the otiter pigment layer {pi(j.') in some portions of the eye ; 

 in the second place, as is shown in the figures, and has already been 

 mentioned, the outer layer is directly continuous with the pigment layer 

 of the retina, Avhich of course it should not be if it belongs to the 

 cornea ; and, in the third place, the inner layer of the cornea is itself 

 present and not pigmented (Figs. 6 and 7, cru.). 



Concerning the condition of the retina in this eye I speak with con- 

 siderable hesitation, because of a fear that its peculiarities may be due to 

 artificial canses. T should say, however, that the specimen was hard- 

 ened in chromic acid, and that all the tissues around the eye are well 



