INTESTINAL RESPIRATION IN ANNELIDS. 797 



shallow dish and only partly covered with water, so that, while the anus is immersed, 

 the back projects above the surface, it can be seen, by carefully inspecting the dorsal 

 surface, that each expulsion of water is accompanied by a depression of the middle of 

 the animal's back, in the middle third or in the third quarter of the body, reckoning 

 from the front. In the intervals this region slowly arches itself and becomes slightly 

 convex, to become fiat or slightly concave again at the expulsion of the next jet. The 

 mechanism of expulsion would seem to be the contraction of the muscles of the body- 

 wall, especially those of the dorsum. 



Direct proof that the water is taken in at the mouth is furnished by the following 

 experiment : — The anterior part only of an animal, which previously was ejecting quite 

 colourless water from its anus, was immersed in carmine water for fifteen minutes. 

 It was then washed and put in clean water ; ten jets of carmine-tinted water were then 

 expelled from the anus. The water in the dish was then changed ; similarly after four 

 more jets, and again after four more. The tint of the expelled water was now growing 

 fainter, and after the water had been again replaced, and three more jets had occurred, 

 no colour was perceptible. Another similar experiment gave similar results. 



Darboux (13), investigating the alimentary canal oi Aphrodite, found no solid food 

 in the intestinal diverticula ; Setti (44), however, found traces of solid matter. Later, 

 Jordan (26) agrees with Darboux that no solid food enters the diverticula. We may 

 therefore conclude, from these observations and those recorded above, that respiration 

 by means of the alimentary tract is a prominent feature in Aphrodite 

 aculeata ; it takes place in a peculiar manner, by the introduction of water in 

 considerable quantity at the mouth, and its passage through the alimentary 

 canal, from which it is ejected in jets by the anus. The intestinal caeca 

 probably act as reservoirs of the ingested water; and its expulsion is effected 

 principally by the muscles of the dorsal body-wall. 



Other AphroditiddB. 



A number of small Polynoids were examined microscopically, and experiments 

 with carmine in suspension were carried out on Halosydna gelatinosa, a larger 

 species, but the results were in all cases negative. 



Phyllodocidse. 



I have observed a large number of Phyllodocids, mostly small specimens suitable 

 for microscopic examination. In none, however, was any sign of ascending ciliary 

 action to be seen ; carmine experiments also gave negative results. 



Antiperistalsis was observed on one occasion only, and then only slightly ; a few 

 feeble antiperistaltic contractions extended over two or three segments in the posterior 

 part of the body ; they were irregular in rhythm, and soon ceased. 



