404 
Dr. 0. Burger on the 
Carinina . 
Carinella. 
Enopla. Group II. 
The central nervous system is divided into a brain and 
lateral cords. In addition to the swollen anterior portion of 
the lateral cords, which forms the ventral ganglia, the brain 
always shows traces of a pair of dorsal ganglia, which, in the 
highest forms, far exceed the ventral ganglia in size, while 
the degree to which they are developed appears to depend to 
a certain extent on the development of the lateral organs. 
This is proved by the most primitive forms, in which both 
lateral organs and dorsal ganglia are of simple structure and 
small size. In the higher forms, however, in which the 
lateral pits are reduced in size, as we have found to be the 
case in Prosadenoporus , the dorsal ganglia by no means 
undergo a corresponding reduction. The ganglia of the 
brain are united by a dorsal commissure, which passes above 
the rhynchodseum in Carinella and above the rhynchocoelom 
in Cerebratulus and Drepanophorus. A ventral commissure 
passes below the rhynchocoelom and in the Enopla lies upon 
the fore-gut. The position of the brain is consequently by 
no means absolutely constant even in this respect. Many 
Nemertines have been shown to possess an anal commissure 
connecting the two nerve-cords. The central nervous system 
possesses a variously constituted sheath of ganglion- cells, 
which differ exceedingly in form, according to the particular 
region of the brain, and are eminently characteristic of the 
various regions. The brain and lateral nerve-cords of certain 
representatives of Group II. ( Cerebratulus and Langia) 
possess neurochord -cells and branched neurochords, which 
traverse the central substance of the lateral cords. Represen- 
tatives of Group III. [Drepanophorus and Prosadenoporus) 
