230 ARTHUR E. SHIPLEY. 



and is, I believe, maintained as a constant flow by the action 

 of the cilia lining the ciliated groove which runs along one 

 side of the ascending intestine. This groove is lined by cells 

 bearing strong cilia. I have never seen any trace of food in it ; 

 and its chief function is, I think, to maintain the current of 

 water which passes through the alimentary canal. 



Professor Semper, in his ' Animal Life,' has drawn atten- 

 tion to those animals which breathe through their intestine. He 

 has described certain foliated processes on the stomach of a 

 Holothurian — Stichopus variegatus — which function as 

 gills; he also mentions the common loach, Cobitis fossilis, 

 which breathes through its stomach, but in this case it 

 swallows air from the surface of the water. This air " is de- 

 prived of a portion of its oxygen in the intestine." Certain 

 Brazilian fish, of the genera Calichthys, Doras, and Hypo- 

 stomus, which also swallow air, have curious processes or folds 

 of the lining of the intestine, which have been regarded as 

 especially adapted for respiration. The anal respiration, 

 which Professor Hartog has described in so many Crustacea 

 and insect larvae, is but another example of the alimentary 

 canal being used as a respiratory organ. These instances are 

 sufficient to show that in ascribing a respiratory function to 

 the alimentary canal of Sipunculids one is supported by 

 numerous analogous cases. 



The Generative Organs. 



Onchnesoma, like other Sipunculids, is dioecious. The testes 

 are formed by the growth of a small clump of cells lining the 

 coelomic cavity in the neighbourhood of the point of origin of 

 the single retractor muscle (fig. 7). I have not been able to 

 find any ovary, though I suspect that when mature it is to be 

 found in the same situation. Numerous ova were found float- 

 ing in the coelomic fluid of the females ; but, as Koren and 

 Danielssen have remarked, " while the ova continue their 

 development in the perivisceral cavity, the last vestiges of the 

 ovary disappear entirely, so that no trace of it remains." 



Like the ova, the spermatozoa undergo a considerable de- 



