ON AMPHILINA PARAGONOPORA 67 



in his description of the general plan of the excretory system 

 and admits that his preparations were ill adapted to show even 

 the central nervous system ; and Cohn, as we have seen, 

 suggested that Salensky's ' problematic ' cells were themselves 

 the flame-cells ! I may add, finally, that I was also unable 

 to detect cilia in any of the excretory canals. 



(e) The Central Nervous System. 



In 1874 Salensky remarked upon the presence in Amphi- 

 1 i n a f 1 i a c e a of two longitudinal nerve-trunks, and Lang (4) 

 in 1881 confirmed this, and also described a ' brain com- 

 missure ' (a liand of fibres piercing the boring muscle) and 

 branches given off from the two lateral longitudinal trunks. 

 Cohn in 1904 added the information that the branches given 

 off dorsally and ventrally from each of the two lateral longitu- 

 dinal trunks meet dorsally and ventrally across the body so 

 as to form a series of nerve-rings throughout the length of the 

 body, but since these rings were not observed by Lang, and 

 are certainly not present in the elongated and more nearly 

 cylindrical A. paragonopora, T doubt their existence. 

 PI. 4, iig. 29 illustrates the anterior end of the central nervous 

 system in A. paragonopora, and it will be seen that it 

 confirms Lang's description in all respects. Anterior to the 

 ' brain commissure ' the two lateral longitudinal trunks extend 

 forwards and end in the margin of the anterior end of the 

 body. Posteriorly, in A. paragonopora, the two lateral 

 longitudinal trunks converge slightly (in accordance with the 

 narrowing of the body) but do not appear to join : they 

 terminate separately at the sides of the posterior inlet or 

 semicircular bay at the posterior end, in much the same way 

 as the trunks terminate anteriorly. In transverse and longitu- 

 dinal sections each of the lateral longitudinal trunks is seen to 

 give off dorsal, ventral, and internal branches (Pis. 3, 4, figs. 4, 5, 

 29), and these are distributed to the body-wall muscles and 

 other organs. I have not ascertained the exact numbers of 

 these branches. The trunks are uniform in diameter and 

 there are no special aggregations of ganglion cells. 



F 2 



