16 THOS. H. MONTGOMERY, 



the body wall (Fig, 22); and a similar discontinuous layer is found 

 around portions of the intestine. These layers may be termed pseudo- 

 epithelia, to use the word advocated by Hatschek (Lehrbuch der 

 Zoologie, '88, p. 113). Bürger ('90) compares these layers to the 

 splanchnopleura and somatopleura decribed by Salensky ('84) for 

 Monopora, but the latter genus is Metanemertean, where the layer 

 termed "somatopleure" encloses the nerve chord ; and it is further 

 probable that in Motiopora, as I shall show to be the case in the 

 Metanemertean genera examined by me, the layers are differentiations 

 of the connective tissue with intercellular substance, and not mesen- 

 chym tissue as in Cerebratulus. 



There are found in the body cavity, further, free-floating cells, 

 which difier from the other mesenchym cells, in having no cell fibres, 

 the nucleus being simply enclosed in a spherical mass of cytoplasm 

 (Fig. 22 FMes, Fig. 17). 



The cytoplasm of those cells suspending the blood vessels, and in 

 fact of most of the mesenchym cells transversing the body cavity, and 

 fixed at both ends, is usually very finely alveolar, and stains a faint 

 pink with the Ehrlich-Biondi stain. But on the contrary, the cyto- 

 plasm of the free-floating cells, as well as many of those constituting 

 the outer pseudoepithelium, may be filled to greater or less extent 

 with small granules (Figs. 17, 22 Nutr), which stain a deep red. All 

 intermediate stages are found between cells, in which only a few 

 granules occur near the nucleus, and such, in which not only the 

 cytoplasm, but also the nucleus itself is filled with granules, causing 

 a corresponding increase in the size of the cell and its nucleus. It is 

 very probable that the accumulation of these granules in the cells 

 represent nutritive processes, similar to those which Korschelt ('89) 

 has described for Insect ova, and other objects. Many of both the 

 free-floating cells, and the cells of the outer pseudoepithelium present 

 amitotic division stages — dumbbell shaped nuclei, two nuclei in one 

 cell, etc.; and all cells in such division contain nutritive particles. 

 At occasional distances along the outer (apparently never the inner) 

 pseudoepithelium, one finds, on a section, 4 to 6 cells in a row, which 

 have about ten times the bulk of the surrounding cells, owing to 

 their great accumulation of nutritive particles, and which are also in 

 various states of amitotic division (Fig. 22); the fact that such cells 

 are more or less spherical in shape, owing perhaps to a retraction of 

 their fibres, and the fact of their evincing cleavage stages, leads me 

 to the assumption, that by their divisions the free-floating, spherical 



