IÇI5-] Fauna of the Chilka Lake : Coelenterates. 93 



but is usually tinged more or less deeply with olive-green ; sometimes the endoderm 

 of the tentacles is marked with alternate green and white rings, the pale rings being 

 narrower than the dark. The most characteristic features in the colouration is, 

 however, a series of eight blackish vertical bars that ornament the capitulum just 

 below the disk, one outside each mesentery. Each bar is double, being completely 

 bisected longitudinally by a colourless or pale line, and expands at the upper end, 

 which is sometimes separated as a distinct spot or rather pair of spots. The scaphus 

 has a bright orange-scarlet colour, which, unlike the markings of the capitulum, 

 retains its intensity in spirit ; this colour is not intrinsic in the tissues of the animal 

 but due to a staining of the particles of mud incorporated in the delicate " cuticle" 

 that clothes the scaphus. 1 The physa, both in living and in preserved specimens, is 

 of a fairly opaque white. 



The tubercles on the scaphus are a characteristic feature of the species, not only 

 on account of their prominent nature but also of their internal structure. In most 

 sections of the column they appear merely as hollow outgrowths of the wall due 

 mainly to a thickening of the mesogloea accompanied by the apparent formation of 

 a large lacuna ; but if specimens of the whole animal be mounted for microscopic 

 examination after being rendered transparent it will be readily seen that each lacuna 

 contains, in addition to a quantity of mucus, what appear to be a number of long 

 slender chaetae arranged for the most part almost at right angles to the circum- 

 ference of the column but converging somewhat to the tip of the papilla, which con- 

 tains a minute aperture. In a few sections of several large series some of these 

 peculiar bodies remain in situ and can be recognized in the slender nematocysts of 

 the type figured more than fifty years ago by Gosse in his Actinologia Britannica 

 (pi. xi, fig. 10, i860). Their threads can be occasionally detected emerging from 

 the pore in the papilla (pi. vii, figs. 5, 5«). The cavity of the tubercle has a diameter 

 of about O'oo, mm. 



The body-wall is very thin in the capitulum, but considerably thicker in the 

 scaphus, the difference lying mainly in the relative amount of mesogloea present ; 

 in the physa the mesogloea is thin but the endoderm rather thick. There is no 

 special sphincter, but the circular muscle, which lies at the base of the endoderm, is 

 well developed both in the scaphus and in the physa. The nervous layer is well 

 developed. The wall of the tentacles is thick, but their mesogloea relatively thin. 



The stomodaeum is ample at its upper extremity, occupying in its longer axis 

 more than half of the diameter of the column and having a rather narrowly oval 

 shape in cross - section ; it is very short vertically and does not quite reach the 

 lower end of the capitulum. 



There are, in addition to the usual eight complete mesenteries, eight rudimentary 

 ones, but these are confined to the upper part of the stomodaeum. They have the 

 arrangement apparently normal in the genus, i.e. there are two in each sulco-lateral 



1 A similar staining of muddy particles is often produced at the edge of the mantle in some of the 

 Chilka Lamellibranchs {e.g. Theora opalina) and in the tubes of Maldanid worms. 



