62 OPINIONS AND DISCOVERIES 



These expansions and filaments are developed and disap- 

 pear in irregidai' successions, regulated in some degree by 

 the temperatore, for a high temperature acts as a stimulus 

 upon them, while cold considerably retards the vai'ied 

 changes. WTien the globides miite into a small parcel or 

 mass the power of locomotion in it ceases, but the edges 

 continue to exhibit the same changes in their outline. In 

 these masses we discover some coloured gi-anules, green in 

 spring, and grey or yellowish at a later season, which Du- 

 jardin does not believe to be ovules or seminal, but rather 

 of foreisrn and accidental origin, similar to those which tinge 

 the animalcules of coloured infusions. 



From the chai-acter of their gelatinous granules and 

 masses Dujardin entertains no doubt of the animalit}- of 

 sponges, for he had previously discovered that the Amibes, 

 and some microscopic multilocular shells, did emit a like 

 glutinous fluid endowed %vith precisely the same pro- 

 perties.* 



The experiments of Dutrochet, Gervais. and ^Ir John 

 Hogg having been confined to the fresh-water sponge (iS^ow- 

 ffilla), I shall defer giving the results of them uutil that 

 genus comes imder oiu* special consideration. It may suf- 

 fice to state in this place that these naturalists have been 

 led to the conclusion that the Spongilla belongs of right to 

 the vegetable kingdom. ^^Tien ]Mr Hogg began the study 

 of zoophytes, he participated in the then prevalent opinion 

 of the animalit}" of sponges in general, and deeming the 

 organic mucus to be the most essential paii in their struc- 

 ture, he instituted for them a distinct order in their class, 

 which he termed Gelatinifern, on piu^ose to express this 



* Ann. dps So. Nat. n. s. x. p. 5. &e. 



