1863."] DR. J. S. BOWERBANK ON THE SPONGILLlDiB. 459 



penetrate the outer membrane ; and until the ovary has been ren- 

 dered transparent by the aid of boiUng for a few seconds in nitric 

 acid, they are completely immersed in the tissues. They are disposed 

 in a single layer, but are so closely packed together that their mar- 

 gins frequently overlap to a considerable extent. The form of the 

 Bcutulum is truly that of a little shield, the lower surface being con- 

 cave, while the upper one has a corresponding degree of convexity, 

 and the umbo projects from its centre in the form of a small cone. 

 The diameter of an average-sized one was y^Vo i"ch, and the height 

 very nearly equalled the diameter. 



Spongilla Batesii, Bowerbank. 



Sponge massive, sessile ; surface spiniferous ; superficial inter- 

 spaces open. Oscula, pores, and dermal membrane obsolete. Ske- 

 leton-spicula fusiformi-acerate, large, and stout. Ovaries spherical, 

 spiculous, encased in an irregular but very open reticulate envelope ; 

 spicula of envelope acerate, stout, slightly curved. Ovary-surface 

 tuberculate ; tubercles short and very broad. Spicula of the ovaries, 

 of exterior surface fusiformi-acerate, entirely spined, minute ; spines 

 of the middle portion large, cylindrical, terminations obtuse. Spicula 

 of the interior surface umbonato-scutulate, minute. 



Colour, dried state, pallid green. 



Hab. River Tapajos, tributary to the Amazon, on the pendent 

 branches of trees {Mr. Bates) . 



Examined in the dried state. 



I received three fine specimens of this species from Mr. Bates. 

 He describes them as being " found attached to stems and branches 

 of trees which are submerged for three months in the wet season," 

 and that " they are plentiful in the deep gloomy ygapos." The three 

 specimens are very similar in form and dimensions, being of the size 

 and shape of a common fowl's egg. Two of them only partially 

 embrace the stems on which they are seated ; the third entirely sur- 

 rounds it. One of the specimens is evidently young ; it is of a lighter 

 green colour than the others, uniform in its structure, and has but 

 few gemmules ; and several of these are small and not fully deve- 

 loped. In the other two the greater part of the skeleton of each is 

 brown, and has a dead appearance ; and this portion is totally desti- 

 tute of gemmules. United organically to the dead portions of the 

 two Sponges, there are in each one or two patches of the skeleton 

 which were evidently in a living state when collected. They are of 

 a fresh dark green colour, and abound with mature ovaries ; so that 

 it would appear that the species is so far an annual that when the 

 portion produced at one period has fulfilled the important offices of 

 reproduction, and has shed its ovaries, its existence is then termi- 

 nated. 



The surface of the Sponge is strongly and rigidly spiniferous, and 

 the superficial interspaces large and open, without the slightest 

 vestige of either investing membrane or reticular structure to close 

 the apertures. 



The ovaries are not immediately at the surface, but a slight distance 



