430 MONTGOMERY. [Vol. XIII. 



11. Ganglion cell III has structural affinities on the one 

 hand to II, on the other to IV ; these three are probably motor 

 cells. 



12. In the fibrous core representing the so-called dotted 

 substance the following components may be distinguished : 

 (i) staining, dense, branching fibres of the inner neuroglia cells, 

 these being the only fibrillar constituents of the dotted sub- 

 stance ; (2) nerve tubules and their sheaths ; (3) irregular, 

 branching spaces filled with body fluid. In the lateral chord 

 of Linetis is situated a longitudinally directed nerve tube near 

 the center of the fibrous core, composed of a large number of 

 individual nerve tubules. This nerve tube gives off smaller 

 nerve tubes which pass to the peripheral nervous system ; an- 

 teriorly it is not continued into the brain. By no means all, 

 probably not half, of the nerve tubules in the fibrous core are 

 enclosed in this nerve tube, since a large number are distrib- 

 uted pretty evenly throughout the fibrous core. 



13. The fibres of the outer neuroglia cells produce not only 

 loose sheaths around the ganglion cells III and IV, but are also 

 continued distally to form a sheath of Schwann around the 

 nerve tubule ; this sheath, which is never occupied by nuclei, 

 is not a continuous membrane, but apparently consists of a 

 single layer of parallel fibres, which are separated from one 

 another. The neuroglia of the nemerteans is fully comparable 

 to that of the annelids or vertebrates, and stands in no rela- 

 tionship to the elements of the neurilemmatic sheaths, 



14. In Cerebratulus and Linens gesserensis there is a second 

 ventral commissure of the brain uniting the ventral lobes, situ- 

 ated behind the first massive commissure, and of much smaller 

 diameter. In L. sp. there is, in addition to the second, also a 

 third ventral commissure. 



15. In Cerebratulus there are three commissures of the 

 oesophageal nerves, the third (most posterior) being the largest. 

 In Linens there are four such commissures, the fourth of which 

 is the largest, corresponding to the third of Cerebratulus. 



At the close of this brief study of the elements of the central 

 nervous system of Linens and Cercbratiilus it is not my inten- 

 tion to enter into a discussion of the many views in regard to 



