492 F. VV. GAMBLE AND J. H. ASHWORTH. 



cliaracteristic fibrillar network whicli arises from tlie outer 

 fibrous sbeatb. The chief difference, moreover, between 

 them and true ganglion-cells lies, according to Apathy, in 

 the number and arrangement of the neuro-fibrillae : these 

 specially large glia-cells only possessing a few fibrillsa 

 ■which do not exhibit the formation of a network by the 

 ingoing fibrils, and recombination to form outgoing ones. 

 In other respects — in their position in the mid-ventral line of 

 the cord, in their size (70 to 80 ju diam.) — they superficially 

 resemble the multipolar ganglion cells, with which indeed 

 they have previously been confused by the earlier writers on 

 the Hirudinean nervous system. 



We have compared Apathy's description (unfortunately he 

 has hitherto published no figures) of these " Sternzellen " 

 with the appearances exhibited by the giant-cells of Areni- 

 cola, and we find that the giant-cells differ in being unipolar, 

 in the nature of their single process, and in the number and 

 arrangements of the neuro-fibrillee, while they conform in all 

 these points with ganglion-cells. 



Accordingly we feel justified in considering each giant- 

 cell, its process and branches, as a distinct nerve element of 

 the cord. 



The doubt which has been hitherto felt by many anatomists, 

 and which is still widely shared, as to whether the giant-fibre 

 is a process of the giant-cell, and whether it is nervous in 

 function, arises partly through the negative reply given by 

 Retzius (1891) and von Lenhossek (1892), and partly by the 

 lack of analogy of the giant-fibres with any recognised nerve 

 element either in their structure or in their relation, or rather 

 want of relation, to the rest of the nerve-cord. It is urged 

 that every important nervous structure in the cord of Lum- 

 bricus can be demonstrated by the Grolgi method, but that 

 the giant-cells and fibres cannot be impregnated ; and it is 

 held that this failure of the method in the hands of such 

 competent histologists as Retzius and Lenhossek is sufficient 

 to show that these cells and fibres are other than ordinary 

 nerve elements, if indeed they be nervous. On the other 



