3 Br. Asajiro Oka: 



anterior ends of zooids with a short Ijranchial siphon at the 

 centre. Looked at from inside, each double row of zooids forms 

 a cushion-like ridge projecting into the central cavity and 

 separated from its neighbours by narrow deep furrows. These 

 furrows correspond in position to the shallow longitudinal 

 depressions on the outer surface of the colony. A cross section 

 through the middle of the head has therefore the shape repre- 

 sented in text-fig. 2. Jt consists of thick and thin portions placed 

 alternately in a circle, the former being each a mass of the 

 investing substance containing two rows of zooids, while the 

 latter are nothing but a thin layer of the common test forming 

 the bottom of the deep longitudinal furrows just referred to. As 

 the test and body-wall are transparent the intestines with their 

 dark coloured contents stand out very conspicuously on the inner 

 surface as dark brownish loops (see PI. I., fig. 1). Under a lens 

 the stomach is also very clearly visible. 



Arrangement of zooids. As stated before, the zooids are 

 arranged in longitudinal rows which run distinctly in pairs. In 

 one of the two colonies examined by me there are sixteen of such 

 double rows present, while the other one, which is somewhat 

 smaller, though not much shorter, has only twelve. Each row 

 begins at the very margin of the lateral wall of the head and ends 

 on the basal surface at some distance from the top of the peduncle. 

 The number of zooids which form a longitudinal row is 

 generally twelve or thirteen, not counting a few small buds 

 situated on the basal surface of the head. The zooids in a pair of 

 lines are placed alternately, and as the amount of the test sub- 

 stance intervening between them is proportionally very small, the 

 anterior ends of the zooids are visible externally as hexagonal 

 areas with the branchial siphon projecting from the centre. The 

 whole external surface of the head therefore looks like a 

 pavement composed of equal sized polygons (PI. I., fig. 2) in 

 which, however, the longitudinal rows are grouped in pairs 

 separated from one another by narrow zones free of zooids. 



The thoracic regions of the zooids are as a rule placed nearly 

 at right angles to the outer surface of the colony. At the bound- 



