7ii 



PROFESSOR J. STEPHENSON ON 



direction, and does not seem easy to account for. It may, however, be suggested that 

 the postero-anterior stream of water along the intestinal wall, occasioned by the ciliary 

 movement, must have as its complement an antero-posterior axial stream of water 

 returning to the exterior at the anus, since it is not to be supposed that the postero- 

 anterior current passes through the whole length of the animal and out at the mouth ; 

 and it is possible that the rotation about an axis of the matter in the intestinal canal 

 may be in some way due to the combined action of these two currents. Harmer (23) 

 describes a rotatory movement of the faeces in the Polyzoa as being due to the intes- 

 tinal cilia. 



The faeces may pass out at the anus without the ascending ciliary action being 

 suspended — a demonstration of the axial antero-posterior stream assumed above. 



Summary. 



The following list includes all the Microdrili which I have hitherto examined with 

 reference to these phenomena ; the occurrence of antiperistalsis and ascending ciliary 

 action, or their absence, is noted against each : — 





Antiperistalsis. 



Ascending 

 Ciliary Action. 



Naidid^ — 







Nais communis Piguet, var. punjahensis 







Steph 



Yes. 



Yes. 



Slavina punjahensis Steph. 







Yes. 



Yes. 



Branchiochilus Iwrteiisis (Stepli.) 







Yes. 



Yes. 



Prisiiria longiseta Ehrbg. . 







Yes. 



Yes. 



,, xquiseta 'Qowxne.l . 







Yes. 



Yes. 



Stylaria lacustris (L.) 







Yes. 



Yes. 



Aulophorus tonkinensis (Vejd.) . 







Yes. 



Yes. 



Dero sp. i. 







Yes. 



Yes. 



„ sp. ii 







Yes. 



Yes. 



Nais Paraguay ensis Mchlsn. 







Yes. 



? 



Naidinm sp. . 







Yes. 



1. 



Chsitogaster punjahensis Steph. . 







No. 



No. 



,, orientalis Steph. 







No. 



No. 



TUBIPICID^ — 







Limnodrilus socialis Stej^h. 



Yes. 



Yes. 



Clitellio are7iarius (Miill.) .... 



Yes. 



Yes. 



BrancMura sotverbyi Bedd. 



Yes. 



No. 



Enchytr.eid^ — 







Numerous species ..... 



Yes. 



No.* 



^OLOSOMATIDVE — 







jEolosoma viride Steph .... 



Yes. 



Yes. 



,, hemjnichi Ehrbg. 



Yes. 



Yes. 



Except in a single specimen of Friderieia bulbosa. 



