ANATOMY AND CLASSIFICATION OF THE ARENICOLlDiE. 497 



think, beyond doubt), then Apathy's interpretation of giant- 

 fibres as " sensory " can hardly be accepted. What is 

 wanted more than anything else to settle the question is 

 an investigation of their peripheral ending by a physiolo- 

 gical method, such as the results of section of the giant- 

 fibres, and of the destruction of the giant-cells. 



While, at any rate, one result (the exit of fibrils to the 

 cord) obtained by Cerfontaine (1892) by the use of methy- 

 lene-blue on the giant-fibres of the earthworm has thus, 

 at Apathy's hands, received confirmation, there has been no 

 corresponding confirmatory work in Polychastes. The ten- 

 dency of recent research has certainly been to accept the 

 continuity of giant-cells and some element of the giant- 

 fibres; but beyond the fine lateral branching of these fibres 

 observed by Eisig (1887) and Friedlander (1899), in Masto- 

 branchus (CapitellidaB), there has been no proof of entrance 

 of the processes into the spinal nerves, nor has any complete 

 analogy been drawn between the giant-fibres of Polychaetes 

 and ordinary nerve-elements. This discordance is most 

 plainly seen in the rarity of statements to the effect that 

 any connection exists between the giant-fibres and the cord 

 itself. Hamaker (1898), however, lias shown that in Nereis 

 the giant-fibres are pierced by ordinary nerve-fibres (especially 

 by his "set B "j on their course to the periphery. A com- 

 parison of Hamaker's fibres ("set B") with Apathy's " sen- 

 sorische Schliiuche " in leeches suggests, however, that these 

 fibres are part of the same set of elements to which the 

 giant-fibre itself belongs : and further, that processes of indi- 

 vidual giant-cells, which in other Polychaetes, form an appa- 

 rently continuous giant-fibre, may in reality represent a 

 number of fibres, which though auastomosing and decussat- 

 ing, yet ultimately escape from the giant-fibre into a spinal 

 nerve without the adjacent fibrils or axis-cylinders under- 

 going the intimate anatomical continuity which is sometimes 

 stated to occur. 



At this point the evidence we have obtained from Areni- 

 cola Grubii has a distinct bearing on the problem. We 



