58 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



do not see how we can avoid the conclusion that these axial fibers 

 of the prism and pyramid cells are somehow concerned in vision. 

 In Patten's theory these fibers would represent a conducting element, 

 the real sensory element (fibrils perpendicular to these axial fibers) 

 not having been demonstrated by me. 



I have recently read in a short review of Patten's theory 9 that 

 the evidence we at present have points to the tips of the cones 

 (vertebrate eye) as being the seat of the sensation of red. This would 

 be exactly the converse of what Patten's theory supposes. Whether 

 or not this objection is a real one, future investigation only can 

 determine. 



Hesse 13 regards the axial fibers that he describes for the rods in 

 worms as the primitive fibers of Apathy. In this I agree with him, 

 regarding the axial fibers I have described as " Primitivfibrillen." 

 Further, I believe, if I understand Apathy rightly, that the fibrils 

 described by Patten as extending laterally from the axial fibers 

 correspond to Apathy's " Elimentarfibrillen." 



It is the long pigment cells that are the puzzling element. Since 

 there can be little doubt but that these cells can project and retract 

 their pigmented parts (as already described), it would seem that a 

 part of their function is to check the diffusion of light in the vitreous 

 body when exposed to strong light. This function would be quite 

 analogous to that of the pigmented cells of the vertebrate retina, 

 which in light become projected between the rods and cones. Similar 

 observations have also been made on the compound eyes of arthropods 

 by Herrick 10 and by Parker 7 , who find that the distal retinula cells of 

 Palaemonetes project themselves distad in the dark, thus surrounding 

 the vitreous cones with a cylinder of pigment, while (Parker) the 

 pigment of the proximal retinula cells migrates centrad and the 

 accessory cells move distad; in light the reverse takes place. Other 

 observations of this kind are not wanting for Crustacea, insects and 

 arachnids. To my knowledge, the pigment changes that I have 

 described are the first of their kind for medusae. 



I suggested while describing the capsule, that the lens might be 

 adjustable. That the fibers of the long pigment cells extend to the 

 lens is my principal reason for this. May these cells not represent 

 ganglion cells and their distad fibers nerve fibers? That they are not 

 sensory (i. e. are stimulated by light waves) seems to be suggested by 

 their not having any axial fiber and in having several centrad pro- 



