1 ^ Dr. Asajiro Oka : 



The body wall is composed inainl}^ of three elements — the 

 ectodermal epithelium, the connective tissue, and the muscular 

 fibres. The ectodermal epithelium is present throughout the 

 whole extent of the mantle and is in direct contact with the test. 

 The cells of this layer are generally flattened (PL II., fig. 7, ect.), 

 especially so in the walls of abdomen where they form a thin 

 pavement epithelium, but at the margin of the branchial siphon 

 they are considerably thicker and almost cubical in shape (PL II., 

 fig. 9, ect.). The connective tissue is present in the form of a 

 hyaline homogeneous mass containing scattered cells and per- 

 forated by blood spaces. The cells are fusiform or stellate in form 

 and have distinct nuclei. The stellate cells are found generally in 

 such places where the layer of connective tissue is rather thick, 

 and are then scattered equally all over. Where the connective 

 tissue forms a thin layer more fusiform cells are met with, some- 

 times with their longer axes perpendicular to the plane of the 

 adjacent ectodermal epithelium. 



The musculature is on the whole very feebly developed. 

 Over the abdomen not a fibre is visible, and on the thorax the 

 body wall has only a few scattered fibres here and there except on 

 the anterior surface where they are more numerous. In the wall 

 of the branchial siphon the fibres are placed transversely, forming 

 a sort of sphincter round the external opening. Longitudinal 

 fibres are also present, but are much less numerous. Compact 

 bands of muscle fibres, such as are frequently met with in other 

 genera, do not occur in any part of the body wall. 



Branchial sac. This organ occupies tlie greater part of the 

 thorax, and is only partly covered by the body wall. When fully 

 expanded it is somewhat barrel-shaped and extends from the 

 anterior wall to the basal part of the thorax (PL I., fig. 3, hr. s.) 

 In most zooids examined by me the branchial sac was strongly 

 contracted, and it was with great difficulty that the exact form and 

 structure of the organ could be made out. In a few exceptional 

 cases, however, it could be satifactorily observed under a dissect- 

 ing microscope. 



The endostyle runs along the ventral, and the row of languets 



