204 PATTEN. [Vol. I, 



spond in number with the nerve-spindles of the retinal ganglion 

 and with the ommatidia. 



The outer medulla is composed of concentric layers of fibres, 

 those of adjacent layers being at right angles with each other. 

 These layers are crossed at right angles by those fibres just de- 

 scribed, and by the inward prolongation of the stalks of those 

 ganglion-cells which form the cortical layer of the optic gan- 

 glion. 



In every case where it is possible to distinguish anything with 

 certainty the outer medulla can be resolved into single fibres 

 running in different directions in adjacent layers, but not uniting 

 with one another by anastomosing fibrillae. Nothing like the con- 

 fused net-work of anastomosing fibrillae, or "neurospongium," 

 described by Hickson in Musca, has been seen in Vespa, except 

 indeed, in poorly preserved specimens, where the medullary sub- 

 stance has coagulated into a homogeneous and finely granular 

 mass which has some such appearance as Hickson describes. 

 The same remarks apply to the nerve-spindles of the retinal 

 ganglion. I have seen the hazy appearance of the nerve-spindles 

 when macerated and preserved in glycerine ; but believe that 

 it is due to a partial coagulation of the fibrillae composing them, 

 for fresh specimens teased in weak chromic acid show no such 

 appearance. Hickson proposes a new name for the widely 

 present *' granular matrix " in the optic, and other ganglia of 

 the body; for he says, p. 219, although "very commonly met 

 with in the animal kingdom," it has not, as far as he is aware, 

 received any separate name. The very fine "granular matrix" 

 he has reference to is the celebrated " Punktsubstanz " of 

 Leydig (2.) It has also been variously designated by later 

 authors, who have treated this or kindred subjects. 



Dujardin (i), according to Berger, first described this sub- 

 stance in the mushroom bodies of the Bee as the " gramd'dre 

 substanz," and the cell-covering of the same as the " substance 

 corticate piilpeiisey Subsequently, Leydig {2) demonstrated 

 the cellular nature of the latter substance, and showed that the 

 former, which he named the " Punktsubstanz,'' was present in 

 the ganglia of the ventral nerve-cord as well. Dietl (4) 

 called the same substance '^ Marksubstanz," and Berger(6), 

 in his pioneer work on the brain and optic ganglia of Arthropods, 

 used the same term, and called that part in the epiopticon of 



