Notes on the morphology of the Tunicata. 



513 



epithelial cells and their loose fibrous basement membrane, one ob- 

 serves a considerable number of cells slightly larger than the gland 

 cells, whose cell body is filled with numerous yellow granules. (These 

 are not shown in the figures.) Their appearance suggests that they 

 may be leucocytes ^). A few granular cells of a similar size, but with 

 the granules less yellow, are found among the loose cells in the lumen 

 of the gland. They are especially numerous in and around the en- 

 larged portion of the duct near its point of innervation. The ar- 

 rangement of the cells of the outer wall of the gland is so loose that 

 wandering cells might easily pass between them, and probably these 

 granular cells do so, either to devour the disintegrating cells in the 

 lumen of the gland, or else themselves to degenerate with the latter 

 to form the secretion of the gland. I do not find evidence in this 

 species or in any other, that the neural gland is occupied in the 

 formation of blood corpuscles. 



There is a very slight fusion between the ganglion and the gland 

 at several points near the middle of their extent. 



There is no prolongation of the gland into the dorsal raphe. 



A rapheal nerve is present (Fig. 19 r.n). A cord of ganglion 

 cells and nerve fibres arising from the posterior end of the ganglion 





7^ji 



:n 



Uf 



x 





^^sftrnmi^ 



^pr 



Fig. E. A section through the rapheal nerve of BoUenia reniformis, showing how it 

 is surrounded by the fibres of the rapheal muscle. Only a part of the rapheal muscle 

 is shown. The nerve cells are in black with white nuclei. The nuclei of the muscle 

 fibres are indicated by small angular black dots. X ^^^ diameters. 



1) They also closely resemble the phosphorescent cells of other 

 Tunicates, which in all cases lie in blood sinuses, and are apparently 

 modified leucocytes. 



34* 



