256 



TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



neurilemma is broken at intervals by small bundles of 

 axis cylinders from the ganglion cells, which can be traced 

 into the fibrous core. Scattered nuclei are found inside 

 the fibrous core, for the most part just inside the inner 

 neurilemma, though a few may be seen about the centre of 

 it. These are the nuclei of the neuroglial cells, whose 

 branched processes form the supporting groundwork of 

 the nervous system. The fibrous core itself is composed 

 of: — 



(1) Fibres of the neuroglial cells, which stain with 

 many reagents (e.g., eosin), and compose the bulk of the 

 core. 



(2) Nerve tubules, consisting of homogeneous axis 

 cylinders which are usually unstained by reagents, and 

 probably in life consist of a semi-fluid substance bounded 

 by a fine spongio-plasmic sheath. These tubules are very 

 small, and are for the most part scattered about inside the 

 fibrous core, though near the centre a large space is seen, 

 more or less circular in outline in transverse section, 

 which is found throughout the whole length of the core, 

 and probably represents a bundle of nerve tubules. 



(3) Irregular spaces containing fluid.* 



Returning now to the general arrangement of the 

 nervous system, it has already been mentioned that the 

 lateral nerve cords dilate anteriorly to form the brain. 

 This structure is composed of a dorsal and a ventral cere- 

 bral ganglion on either side. The ventral ganglion is 

 merely the expanded end of the lateral cords, and it is 



* It should be mentioned that the above view of the nature of the 

 elements of the nervous core is that advocated by Montgomery (loc. cit. 

 p. 428). Burger on the other hand (Die Nemertinen, Fauna und Flora des 

 Golfes von Neapel Bd. XIX., 1895) supposes the densely staining elements, 

 considered to be neuroglial processes on the above view, are the nervous 

 fibrils, and that the so-called nerve tubules are clefts filled with fluid. 



