38 Mr. H. J. Carter on the Anatomy 



intercalated with those of the fibre, thus presenting a beauti- 

 ful appearance under the microscope. 



Lastly, the colour may be. due to the presence of a para- 

 site, as in the cerulean sponge of the rocks here (Budleigh- 

 Salterton), which only appears in patches about half as 

 large as the nail of the finger, but always of a sky-blue colour, 

 possessing a pin-like spicule, and accompanied by a minute 

 Oscillatoria in the form of short bacillar filaments like those 

 colouring the Red Sea, in whose granules the pigment is seated 

 which gives the blue colour to the sponge while fresh, though the 

 blue fades greatly on drying. The green colour in Spongilla 

 also sometimes depends upon the presence of an Anabina, but as 

 often comes from its own granules ; while Halichondria in- 

 crustans is often pervaded and rendered pink by a minute alga 

 whose cells, both fresh and dry, present a beautiful red Flori- 

 dean colour ; indeed the mere contact of a red seaweed with 

 a sponge may be followed by the latter assuming a similar 

 tint. 



The most striking colour which I have seen among the 

 sponges is the carmine of the Suberites Alcyonium purpureum, 

 Lam., from Australia, and Vioa Johnstonii, Sdt., from the 

 Adriatic, whose spicules are very much alike, and in both of 

 which the colour is exquisite and permanent. 



Starch. 



Starch, impalpable, diffuse, or amorphous, and in the common 

 potato form of grains, although much more compressed, is 

 common in Spongilla and probably in sponges generally ; 

 the latter form is even found in the ovum or seed-like body 

 ('Annals,' 1859, vol.iii. p. 334, pi. i. fig. 7). Still it is very 

 necessary, in examining marine sponges for starch, to be sure 

 that the latter does not come from a neighbouring Fucus, 

 whose cells are always pregnant with starch-grains, and very 

 apt to be cut open when minute and intimately connected with 

 the sponge under microscopical examination. 



Size of Sponges. 



Some sponges are always diminutive, others only so when 

 they are young. In some places the same species may be 

 only found in small amorphous fragments, while in others it 

 may attain a large size with definite form. The largest size 

 that a sponge may attain under favourable circumstances (that 

 is, unmolested &c.) is almost indefinite ; so that the size of a 



