Mr. H. J. Carter on Parasites of the Spongida. 165 



colour fades much on drying, but does not altogether dis- 

 appear. 



Scytonema. 



A species of this Alga with its germinating gonidia still 

 retaining their dark yellowish-green colour, is abundant in a 

 specimen of Spongia otahetica in the British Museum, about 

 which there are no remains of sarcode ; so that it was probably 

 after the death of the sponge that this Alga took up its abode 

 there. It is therefore only mentioned here to show that, in 

 describing the parasites of sponges, the circumstances under 

 which they occur sliould not be forgotten ; otherwise much 

 more may be set down than really belongs to such parasi- 

 tism. 



There are also destructive organisms which not only attack 

 the horny parts of the skeleton but the spicules themselves of 

 a sponge after death, such as have been described and figured 

 in the 'Annals ' for 1873 (vol. xii. p. 457, pi. xvi. figs. 8, 9). 



Palmella spongiarum^ Cart. 



In two instances I have found at this place sponges which 

 liave been rendered pink by the presence of a little spherical 

 cell in great abundance, about the size of the human blood- 

 globule, — viz. one in a specimen of Halichondna panicea^ and 

 the other in a specimen of Gliona celata. And on examining it 

 with a microscope, I find that one mode of reproduction is by 

 duplicate division, and that it is enveloped in a mucilage, 

 which, as the Palmella grows and the cells become multiplied, 

 thus extends itself throughout the sponge, and, by th-e im- 

 mense number of its cells, produces the pink colour. The 

 colour fades to a certain extent, but not altogether, on drying, 

 and is changed to green on the addition of liquor potassae, 

 when it becomes very like a green Protococcus. While re- 

 taining the pink colour, it has very much the appearance, 

 under the microscope, of P. nivalis^ but is much smaller. It 

 averages 1- 2400th inch in diameter ; and, not being polymor- 

 phic (that is, not being able to change its spherical form), it 

 cannot be confounded with the ovules of the sponge, espe- 

 cially when of this size. 



? SAPROLEGNIEiE. 

 Spongiophaga communis^ Cart. 1871. 



This is a minute, short, neraatoid filament, with a bulb at 

 each end, which, multiplying to an enormous extent, espe- 



