THE PYGNOGONIDS. 57 



which stains deeply with gentian violet (40). Beyond this there 

 is a slenderer region which continues outwardly (upwards in 

 the figure) into a protoplasmic syncytium. This syncytium 

 lies on the outer part of the middle layer, under the corneal 

 hypodermis. The cell thus obtained shows no trace of the 

 bacilli, but their absence is due to the macerating fluid, which 

 causes them to swell at the sides of the cell. 



Fig. 40 h was the most successful maceration obtained. Parts 

 of three cells — retinal elements — are seen each passing at their 

 outer ends into a common syncytial mass, as in the former case. 

 The upper part of the figure shows a fine fibril running also into 

 the fused protoplasmic part, and this fiber could be traced out- 

 wards into one of the nerve branches running to the eye, and 

 undoubtedly represents the ultimate nerve fibril which passes to 

 the retinal elements. The distribution of the nerve to the outer 

 part of the middle layer, and the bacillus present at the inner 

 ends of the retinal elements, show conclusively that the retina is 

 "inverted"; so that light entering the eye must, before it can 

 penetrate to the sensory end of the retinal elements — the bacillar 

 end— pass through the layer of nerve fibrils and fused proto- 

 plasmic layer of the eye. 



Fig. 41 a and h shows to what an extent some, if not all, of the 

 retinal elements are flattened. In a the spatula-like end of the 

 element is seen, and this shape is due to the swelling of the bacilli 

 at the sides of the retinal cell. In b the same element is shown 

 as rolled over on its side, and is seen to be much narrower 

 in this diameter than in the former. This accords fairly well 

 with the shape of the elements seen in the section of Fig. 36, 

 Plate VII. 



In Fig. 42 three of the retinal elements are seen still in con- 

 tact — two lying above a third, the inner end of which shows 

 through the transparent ends of the others. Two have spatula- 

 shaped ends and the third is for most of its length broader than 

 the others. Each has a nucleus nearer the outer half where the 

 protoplasm swells out the cell, and beyond this the elements 

 taper away to join, no doubt, in the syncytium at the outer part 

 of the eye. 



In Fig. 43 is a portion of the inner end of a retinal cell which 

 was obtained by sulphuric acid and sea-water, and the figure is 



