1884.] 131 [Hyatt. 



must have passed the grains of carmine on to the cells of 

 the mesoderm, because the amoeboid cells of the mesoderm in the 

 immediate vicinity of the flattened epithelium of the supply 

 canals were loaded with grains of carmine, while others more cen- 

 trally situated were clear. The first named transported the grains 

 through the mesoderm wandering to the neighborhood of the 

 ampullae, and the contents became more or less rounded during 

 this process. Von Lendenfeld, therefore, very naturally supposed 

 that the office of the membrane cells was ingestion, that of the 

 wandering cells of the mesoderm digestion and assimilation, and 

 that of the ampullae excretion. 



We have had excellent opportunities for watching the surfaces 

 of the canals in living specimens of Chalinula arbuscula, and never 

 saw anything akin to excretion in these or in the cells of the am- 

 pullae. The granules, which were abundant and highly refractile, 

 may have indicated, as stated by Dr. Arnold Brass, the presence 

 of nutritive matter ; and their abundance in certain cells of the 

 derm and mesoderm seems to support this supposition. 



The lining layer in the supply and cloacal canals was in all its 

 characteristics the equivalent of the ectoderm; it was a thin epi- 

 thelium, with more or less fusiform or irregular cells, which 

 were hardly half the size of the mesoderm cells in living speci- 

 mens and very liable to destruction by rough handling. Thus it 

 often occurred, that the mesoderm cells lying under them, and 

 forming a dermal layer of greater or less thickness, or of only 

 one layer of cells, were uncovered and seemed to replace them. 

 In one specimen the centres of the cells of the endodermal layer 

 were slightly swollen with contained granules, but this was evi- 

 dently exceptional and not a normal condition. 



The cells of the ectoderm were faithfully studied while living 

 and their contents noted in Ascortis fragilis, Halisarca Dujardinii, 

 Microciona prolifera, and several species of Halichondria and 

 especially in Chalinula arbuscula. The coarsest and thickest cells 

 occurred in Halisarca, but even here the outlines were more or 

 less angular, and the membrane was a single layered epithelium, 

 such as has been described by Schultze and others. No inclusions 

 of food were seen in any case examined by us, nor have any been 

 figured, so far as we have seen, by others. In Chal. arbuscula 

 from Annisquam, Mass. (Sci. Guide, no. in, f. 2) where these cells 



