Species o/" Uruguaya, Carter. 9 



•017 millim. in thickness. Thej are disposed in fascicles so as 

 to form a mesliwork precisely of the same character as in the 

 larger forms of the genus, but of much smaller proportions. 

 In one of the two specimens of which I examined the interior 

 there was a single gemmule of about the same size as those 

 of the larger sponges, and furnished with similar amphidisc- 

 spicules, varying only in size. The amphidiscs are '014 

 millim. in height and the rotules '017 millim. in width. 



The close resemblance of the skeletal spicules of these 

 small sponges to those of the envelope enclosing the gemmules 

 of U. Macandreivij their position of growth at the base of the 

 larger species, and the similarity in the form of the gemmules in 

 both, very naturally raise a suspicion whether the pigmy sponges 

 may not be merely peculiarly modified stages of development of 

 the larger, and not independent sponges. On the other hand, 

 they have every appearance of being complete sponges. 

 Their spicules are uniformly cylindrical, and are evidently 

 full-sized, and not young forms of the larger spicules of U. 

 Macandrewi 'j their arrangement in the wall is the same as in 

 the wall of the larger species, whilst it is distinct from the 

 irregular disposition of the spicules of the monticular envelope 

 in U. Macandreioi ; the oscules at their summits are perfectly 

 distinct, and the presence of full-sized gemmules within the 

 cavity of the sponge indicates that it had reached maturity. 



Distribution. Paraguay. Attached to the base of the 

 type specimen of Uruguaya Macandrewi^ now in the British 

 (Natural History) Museum. I have also one specimen 

 growing on a fragment of U. corcdlioides^ Bowbk., sp. 



The genus Uruguaya was provisionally constituted by Mr. 

 Carter on the supposition that gemmules were not developed 

 in the sponges placed in it ; but now that it has been shown 

 that these bodies are present in some, if not in all, the species^ 

 it is necessary to consider whether it can be retained, or 

 whether the forms placed therein should be removed to the 

 genus Meyenia^ Carter, which includes sponges with gem- 

 mules furnished with amphidisc- or birotulate spicules like 

 those in Uruguaya. The classification of the freshwater 

 sponges generally adopted at the present time is that pro- 

 posed by Mr. Carter in his paper on the " History and Clas- 

 sification of the known Species of Spongilla " *. This is 

 admittedly " based chiefly on the spicules of the statoblast," 

 since " the form of the skeleton-spicule is not only always 

 acerate, but almost always more or less alike in all." But 



* Ann. & Mag. Nat. Hist. ser. 5, vol. vii- (1881), pp. 77-107. 



