246 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 larve, 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. 
Tur GENERATIVE ORGANS. 
Onchnesoma, like other Sipunculids, is dicecious. 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 celomic 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- 
