216 



DR. A. A. W. HUBRECHT. 

 FIG I. FS&2. 



Tig. 1. — ^Diagram of the nervous system of Proneonienia. e, cerebrum, 



I lateral, v, ventral longitudinal stems ; s, sublingual commissure. 



It requires further confirmation ^ whether or not at ? there is a 



posterior commissure between the two lateral stems. 



Pig. 2.— The same of Neomenia, copied from Graff (4). Letters as in Fig. 



1. pCf posterior commissure of the lateral stems. 

 I'iG. 3. — The same of Chcetoderma, reconstructed out of the descriptions 



of Graff (3), and Hansen (6). Letters as in Pig. 2. 

 j'iG. 4,. — The same of CJiiton, copied from Spengel (20). Letters as in Fig. 2. 

 In all these diagrams the nerves for the head springing from the cere- 

 brum as well as the peripheral branches are omitted. 



1 Later investigations have already shown such a commissure to be 

 present in Froneomenia. See the postscript to this article. 



