EXPLANATION OF PLATE XVII. 



Fig. 22. General outline of a specimen of Nais paraguayensis, with active 



budding at the posterior end. 

 ,, 23. Ventral seta, oi Nais paraguayensis. 



,, 24. Shorter seta of the dorsal bundles of Nais paraguayensis. 

 ,, 25. General view of Pristina longiseta ; the species is determined by the 



elongated dorsal seta of the third segment of the posterior 



animal, the corresponding setae of the anterior animal having 



probably been damaged. 



