Mr. H. J. Carter on the Nomenclature of Clathrina. 281 



colour, the tips of the surface are deep carmine-red ; and this 

 is owing to the presence of a parasitic cell, of a beautiful car- 

 mine colou^ which, bound together in great numbers by a 

 transparent envelope, pervades the whole of the sponge in 

 little prothalloid masses, appearing here and there on the sur- 

 face in minute botryoidal tubercles of a dark black-brown 

 colour, formed of a congeries of radiating columns of brown 

 cells placed one above the other in their tubular envelopes 

 respectively, the carmine ones on one side in the sponge giving 

 rise to the brown ones in the columns of the botryoidal tubercle 

 on the other. 



This looks very much like a Hildenhrandtia of the fresh- 

 water kind, which I described and figured in 1864 (Journal of 

 Botany, No. XX. p. 225), and which, indeed, is wo Hildenhrandtia 

 at all, but the type of a new genus, if Kiitzing's diagnosis of 

 the fructification of the latter is to be the criterion (Sp. Alg. 

 p. 694) ; for the conceptacle contains neither tetraspores nor 

 paraphyses. 



But, without knowing the import of the botryoidal masses, 

 or whether there is any further development of this organism, 

 I am unable at present to do more than state what I have 

 seen of it, for the guidance of others. 



The cell, while in its prothalloid investments in the body of 

 the sponge, is about 1 -4000th of an inch in diameter, sub- 

 circular, capsular, filled with homogeneous plasma of a beau- 

 tiful pink or carmine colour by transmitted light, growing 

 granular toward the surface, where, from a total absence 

 of definite arrangement in the prothalloid carmine mass, it 

 developes a defined column of cells filled with plasma of a 

 yellowish-brown colour by transmitted light, which, placed 

 together collectively in a radiating form, produces the dark 

 botryoidal tubercles on the surface, varying in diameter below 

 tlie l-48th of an inch. 



Undoubtedly this is a true Algal (?) parasite of Halichon- 

 dria incrustans, which, perhaps, may account for the colour of 

 the specimen sent to Dr. Bowerbank by Mrs. Griffith, and 

 marked as having been " scarlet, but not foetid" (Brit. Spong. 

 vol. ii. p. 251). Be this as it may, it seems to be the first 

 instance on record, and as yet only seen in Halichondria 

 incrustans. 



There is one phenomenon about CInthrina which is very 

 characteristic of the species, and has been alluded to by Dr. 

 Johnston, as just quoted, in such a way that it shows that he 

 must have studied the sponge in its living state, unless in- 

 formed of the fact by others, — viz. that wnen it dies or is put 

 into fresli water, the white colour immediately changes (that 



Ann. (€• Mag. N. Hist. Scr, 4. Vol. vii. 20 



