192 



Mr. A. J. Ellis on Plane Stigmatics. [June 14, 



the outer segment the conversion of light into nerve-force may take 

 place. 



4. The outer granules being the nuclei of the inner cone- and rod-seg- 

 ments, probably maintain the integrity of these as living tissues, and are 

 not directly concerned in their specific functions as organs of perception. 



5. The primitive bacillary fibres are the link by which the cones and 

 rods communicate through the inner granules and ganglion-cells with the 

 optic nerve-fibres. 



6. The smaller inner granules are nuclei of the oblique bacillary fibres 

 in the inner granule-layer ; or they may be small bipolar ganglion-cells, and 

 act specifically on the forces transmitted through the oblique fibres from 

 the cones and rods. The larger inner granules not being distinguishable 

 by any definite structural characters from the smaller cells of the ganglionic 

 layer, may agree with these latter cells in function. 



7. Since the ganglion-cells (of the ganglionic layer) are fewer than the 

 inner granules, and much fewer than the cones and rods, and since it is 

 probable that these latter communicate with the optic nerve-fibres only 

 through the ganglion-cells, it follows that one ganglion-cell probably is in 

 correspondence with more than one inner granule and with several cones 

 and rods. From this it is not an improbable conjecture that the cones and 

 rods are disposed in groups, each of which is represented by one or more 

 ganglion-cells thef unction of which is to connect or coordinate the indi- 

 vidual action of the separate bacillary elements in their groups in a manner 

 analogous to that attributed to the ganglion-cells of the spinal cord by Van 

 der Kolk*. 



8. There is a close general resemblance between the human fovea and 

 that of the chameleon f. 



II. Second Memoir '^On Plane Stigmatics/' By Alexander J. 

 Ellis, F.R.S., F.C.P.S. Received May 26, 1866. 



(Abstract.) 



Let there be two groups of points upon a plane, termed, for distinction, 

 indices and stigmata respectively, bearing such relations to each other 

 that any one index determines the position of n stigmata, and any one 

 stigma determines the position of m indices. The theory of these rela- 

 tions between indices and stigmata constitutes plane stigmatics. Each 

 related pair of index X and stigma Y constitutes a stigmatic point, hence- 

 forth written "the s. point (^y)." The straight lines joining any index 

 with each of its corresponding stigmata are termed ordinates. If, when 



* I have an impression that I have seen this in a German author, but have not been 

 able to find the passage again. 



t H. Miiller, " Ueber das Auge des Chamaleon," Wurzb. naturw. Zeitschr. Bd. iii. 

 S. 36. 



