Mr. H. J. Carter on Parasites of the Spongida. 169 



slightly issuing from the broken ends of a divided filament, 

 where they contrast strongly with the colourless state of the 

 sheath under tiie application of the iodine solution ; sheath 

 circularly corrugated from retraction at this part, and present- 

 ing lines of corrugation on the inner side of a bend, but no 

 septa internally. Contents of the bulb apparently the same 

 as those of the sheath, with the addition of an indistinct 

 nuclear body surrounded by a granular plasma, presenting a 

 vacuole in the centre, but very variable in appearance in these 

 respects, becoming of an amber colour under the effect of 

 iodine, not purple like that of potato-starch &c. Filament 

 sometimes swollen in the larger part by a nuclear body like 

 that of the bulb, and, in like manner, often slightly accu- 

 minate at one point. When dry, highly hygrometric, twist- 

 ing about on tlie field of the microscope on being breathed 

 upon, like the elaters of an Equisetum-S])OYe similarly circum- 

 stanced. 



Hab. Marine. Infesting and destroying the sarcode of 

 many kinds of sponges, especially the Hircinice. 

 Loc. Worldwide. 



Ohs. This parasite is not a commensalist, but a devourer of 

 its host, like the seaweed Thamnocloniumflabelliforme — finally, 

 in the Hircinida, replacing the entire sarcode so as (as before 

 stated) to present a pseudomorph only of these sponges. Some- 

 times a few fibrillar are a little thinner than the others in the 

 rest of the mass ; and in some sponges they are altogether 

 thinner than in others, as in Sarcotragus spinulosus, Sdt., 

 where they are all thinner than in Hircinia variabilis^ Sdt., 

 as seen in tlie type specimens of these sponges respectively 

 in the British Museum ; but this is the only difference that I 

 have observed in them worth noticing in a developmental 

 point of view. The bulb often varies slightly in shape ; and 

 the filament appears to be sometimes once branched ; but in 

 what form the branch terminates I am not able to state, having 

 only observed it once ; besides, these varieties can only be 

 viewed as anomalies. Under no circumstances have I been 

 able to satisfy myself that the contents of the filament are 

 septate. As with the smaller, coreless, horny sponge-fibre, so 

 with this filament, decomposition of the contents of the in- 

 terior leads to the formation of oleaginous globules, which, 

 presenting shades of colour varying from ochraceous yellow to 

 rusty red, cause the tissue formed by them to present these 

 colours respectively. 



Although dyeing with magenta and mounting some of the 

 filaments of a specimen that I possess which has been pre- 

 served in spirit has given the entire form, nothing that I 



