218 



DR. A. A. W. HUBRECHT. 



Chatoderma occupies a corresponding position (3^ 6), is another 

 argument in favour of this view. I feel very much inclined to 

 look upon it as a stage of simplification of a radular arrange- 

 ment rather than as a primitive more simple structure, from 

 which, by gradual differentiation, a radula might be derived. 

 It was elsewhere insisted upon (7) that the complicated structure 

 of the radula in Proneomenia forbids an interpretation in the 

 latter sense of the link which connects these structures in the 

 different genera of Solenogastres. In Neomenia all remains of a 

 radula may safely be said to have disappeared in the . specimens 

 tliat have hitherto been examined ; none of the different authors 



F!G5 



Pig. 5. — Diagram of the digestive tract of Neomenia and Proneomenia, 

 reconstructed from the descriptions of the different authors (7, 13, 22). 

 0, mouth ; a, anus ; d, ciliated median portion of the intestine ; I, 

 lateral caeca, on which the hepatic functions partially devolve. 



Fig. 6. — The same of Chatoderma ; reconstructed after the description of 

 Hansen (6). o and a, as in Fig. 5 ; d, posterior narrowed portion of 

 the intestine ; I, liver. 



Tig. 7. — The same of Chiton, o and a, as in Fig. 5 ; d, the coiled intes- 

 tine ; /, liver. 



