1907.] Records of the I nd'uDi Museitui. fi9 



specimens and fresh ones, in order to be in a position to discuss 

 this skeleton ; but in vain. All that I find is that in some of the 

 individuals examined the coelenteron is to some extent lined with 

 extraneous particles of silica, which also occur in the mud of the 

 ponds and estuary, and that these particles have occasionally been 

 taken into the cells of the endoderm or even into the mesoderm. 

 It is well known that many Actinians protect themselves by ab- 

 sorbing solid extraneous particles in this way, e.g., the Indian 

 species Myradis tubicola, Haddon (6). The calcareous spicule 

 figured by Stoliczka looks very much like that of an Alcyonarian, 

 and some of my specimens of M. schillerianum var. exul, which 

 were taken from the canals of a Sponge, contain undoubted sponge 

 spicules. 



Colour. — 



Such coloration as the two forms of the species possess is practi- 

 cally identical and is due to three factors ; two of these can be 

 readily explained, while the origin of the third is still obscure. 



The most general cause of colour is the presence of zooxanthellae 

 in the cells of the endoderm of the column and tentacles and of the 

 ectoderm of the stomodseum. These bodies agree in form and struc- 

 ture with those found in other Actinians, In the new race of M. 

 schillerianum, and probably also in the typical form, they are not 

 always present. I found at Port Canning in December that they 

 were fairly abundant in individuals from one of the ponds, but 

 were absent from others living in a second pond only divided from 

 the first by a narrow bank. At the same time they were very abun- 

 dant in examples of the typical form from the estuary ; they be 

 came far less numerous in the course of a few weeks in the same 

 individuals, which were placed in an aquarium, but again re- 

 appeared in large numbers in their tissues before two months were 

 past. The distribution of the zooxanthellse in the tissues was found 

 to be by no means constant. In individuals living buried in mud it 

 was not surprising to find them practically confined to the tenta- 

 cles and the upper part of the column. They were also noted occa- 

 sionally in the mesoderm and even the ectoderm of these regions, 

 and I have seen them on several occasions, as did also Stoliczka, ni 

 the cloud of slime and stinging threads shot out from the external 

 surface when the animal was irritated. In the last instance there 

 can be little doubt that they had been squeezed out accidentally. In 

 individuals of the typical form they are as a rule more numerous 

 in the endoderm underlying the sphincter and in that lining the 

 interseptal spaces than elsewhere. They are not altogether absent 

 from the intraseptal spaces, but are sparsely scattered in the cells. 

 To this fact is due in part the presence of the semi-opaque vertical 

 stripes which, in the typical form, represent the intraseptal spaces 

 externally ; but the difference between the character of the endo- 

 derm of these spaces and that of the interseptal ones is also, to 

 some extent, responsible for this element in the coloration. In the 

 pond race, the scarcity of zooxanthellse in the column renders the 



