4G0 Linnccan Society. 



The author has not perceived any trace of animal organization, or 

 the least symptom of sensation, or any powers of contraction and di- 

 latation in this species of sponge, although he has applied to it, when 

 in a fresh and vigorous state, several sorts of powerful stimulants. 



He next showed that no arguments in support of the fancied ani- 

 mality of the Spongilla can be brought forward, either from its smell- 

 ing like carrion or animal matter, or from numerous spiculae being 

 present in its composition. And the manner in which he raised 

 young Spongilla from the seed-like sporidia and locomotive sporules 

 makes it perfectly conclusive that this freshwater sponge cannot be, 

 as Montagu supposed, the nidus of some aquatic insect, although 

 such an opinion might, without those successful experiments, have 

 been somewhat confirmed by the author's discovery of an unknown 

 and anomalous insect, which he has at present only observed inhabit- 

 ing this production. Some specimens of this small insect were ex- 

 hibited, and presented to the Society. 



Mr. Hogg concluded his letter with some general remarks on the 

 nature of the Spongia marina. He stated that hitherto he had al- 

 ways accounted these substances as being principally composed of 

 an animate or live jelly, which was endowed, as some authors af- 

 firmed, with a certain degree of palpitation and contraction, and di- 

 latation, and consequently had, fourteen years ago, instituted for 

 them an order " Gelatinifera," which he arranged the last among 

 the Polyparia Composita. That on becoming convinced by his late re- 

 searches on the river sponge of its vegetability, he began in some mea- 

 sure to concur in the opinion of Montagu, that that substance might 

 probably be quite distinct from the sea sponge, and to think that the 

 latter might still be of an animal nature ; but, on a more recent exa- 

 mination and comparison of the Spongilla with many of the Spongia, 

 he has found that there exist no real grounds for that opinion, and 

 that there scarcely is even a generic difference between them. 



The author then compared the freshwater sponge with the sea 

 sponge, and showed, among other extreme resemblances in their 

 structure and composition, that many of the latter possess similar 

 seed-like bodies or sporidia, as well as the locomotive germ-like bo- 

 dies or sporules which have been described by Dr. Grant. 



Mr. Hogg concludes, if the currents of water do flow in and issue 

 out from the sea sponge, independent of the function of respiration 

 of any marine insect or parasitical animal nestling within it, that 

 then they are caused by the same means which effect the motions of 

 fluids in plants, and that these currents convey nutriment to the in- 

 ner parts of the sponge, after the same manner as food is supplied 



