60 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



describes what he supposes to be muscle fibers just exterior (distal) 

 to the lens, and believes that a contraction of these fibers would 

 have the effect of forcing the lens nearer the retina, or vice 

 versa. His supposition, like mine, needs experimental verification. 

 Hitherto the only instance known of accommodation in the eyes of 

 invertebrates was that described by Beer 17 for Cephalopods. 



The Proximal Complex Eye. With four exceptions, the description 

 and discussion given for the distal complex eye also holds good for 

 the proximal complex eye (Fig. 13). The four exceptions are: the 

 absence of a capsule to the lens; the absence of the long pigment 

 cells ; the absence of the pyramid cells ; and the different relative 

 position of the lens and retina. This eye, then, has a cornea 

 continuous with the epithelium of the sensory club, a lens, in 

 structure and probable origin quite like that described for the distal 

 complex eye, and a retina of prism cells with axial fibers for the 

 prisms. Since Conant 8b has described this eye quite fully, and 

 discussed Schewiakoff's conclusions at length, I shall be brief. 

 Suffice it to say, that Schewiakoff describes two kinds of cells 

 (supporting cells and spindle-shaped visual cells) for the retina of 

 this eye just as he described for the distal complex eye. The 

 vitreous body he likewise describes as being homogeneous and with 

 spaces for the visual rods (fibers) of the visual cells. It is evident 

 that Schewiakoff has interpreted the structure of this eye from 

 analogy with his results on the distal complex eye. Claus likewise 

 has described two kinds of cells for the retina, and the vitreous 

 body as homogeneous. Conant and myself find only one kind of 

 cells in the retina of this eye. The pigmentation that Schewiakoff 

 describes for the vitreous body I believe to have been dissolved in 

 from the pigmented zone of the retina, for I find no regular 

 pigmentation in the vitreous body. Haake's observation, previously 

 noted (p. 42), applies also to the proximal complex eye. 



Conant's evidence for the axial fibers of the prisms was clearly 

 insufficient, so that he did not in this respect complete his Fig. 69. 

 I republish this figure with the prism fibers drawn (Fig. 13). 



Since the long pigment cells are absent my reasons for supposing 

 the lens of this eye to be adjustable vanish. 



Finally, a word on the origin of the lens and the relative 

 position of the lens and retina. The lens and retina in this eye 



