INTESTINAL RESPIRATION IN ANNELIDS. 801 



Opheliid^. 



Ammotrypane aulogaster. 



In this species it is improbable that any considerable amount of respiratory exchange 

 can take place through the integument ; the form is cylindrical, the body is not 

 segmented externally, the parapodia are obscure, and the surface is smooth and shiny 

 and resembles that of a Nematode with its thick cuticular investment. The dorsal 

 cirri function as gills ; but they are simple small finger-like inconspicuous processes. 



The posterior end is peculiarly constituted. It is funnel-shaped, a deep conical 

 depression leading down to the anus ; the mouth of the funnel opens ventralwards. 

 Rathke (39) describes it as follows : — " Uer After stellt eine nach unten off"ene Schaufel 

 dar, deren Rand mit kurzen Cirri besetzt ist ; eine ahnliche Bildung kenne ich nur bei 

 Nais digitata, wo sich jedoch die Schaufel nach oben offnet." I may add that the 

 posterior margin of the funnel is more vascular than the rest, as evidenced by a red 

 blush which marks this region ; the hinder part of the intestine also, in contrast to the 

 rest of the canal, is distinguished by a deep-red blush. 



The carmine experiment gave an interesting result. The funnel was facing upwards 

 during the observation ; into it the carmine particles were gently and equably drawn, 

 and then travelled forwards towards or into the intestine. Some particles travelled in 

 a posterior direction along the upper (in this position) surface of the animal's body for 

 a very considerable distance before doubling over the margin and entering the funnel. 

 The entering current was regular and definite, and some of the particles introduced 

 were of fair size. 



The observation was conducted under the dissecting microscope, and the above 

 appearances were seen on focussing the upper strata of the anal region. On focussing 

 for a lower level, approximately the middle of the funnel, an equally definite and 

 regular return current was observed. At a deeper level again, particles of carmine came 

 into view which had sunk to rest on the lower wall of the funnel ; these were agitated 

 by ciliary action, but I did not note a regular entering current along the lower inner 

 surface of the funnel corresponding to that along the upper. 



There can be no doubt that the entering current is caused by ciliary action ; but 

 the worms are of some size (two inches long), and opaque ; and higher powers than those 

 afi"orded by a dissecting microscope could not be used. Hence the only direct observa- 

 tion of the existence of cilia was that of the agitation of the carmine particles which had 

 sunk on to the lower part of the inner surface of the funnel. 



Arenicolid^. 

 Arenicola ecaudata. 

 This species is too large and opaque for ordinary microscopical examination ; though 

 the observation of small specimens, and even of larger ones by compression between 

 glass plates, will reveal a certain amount of the organisation of the living animal. 



