454 DR. J. S. BOWERBANK ON THE SPONGILLID^. [Nov. 24, 



minute, dispersed. Pores inconspicuous. Dermal membrane obso- 

 lete. Skeleton-spicula subfusiformi-acerate. Ovaria globose ; sur- 

 face even, slightly pitted; enveloping spiculafew, scattered, fusiformi- 

 acerate, entirely spined ; spines minute, conical ; spicula of the walls 

 inequi-birotulate ; rotulse radially lineated, margins entire, shaft cy- 

 lindrical. 



Colour, dried state, light brown. 



Hab. River Amazon, on leaves or branches of trees, occasionally 

 pendent in the water. Near Villa Nova. 



Examined in the dried state. 



This singularly insignificant little species, as it appears from the 

 only specimen I have yet seen, forms a light-brown incrustation, about 

 three-fourths of an inch long, a quarter of an inch wide, and not ex- 

 ceeding half a line in thickness, on a small leaf from one of the stems 

 on which a Spongilla reticulata from the River Amazon was seated. 

 It is firmly attached to the leaf by a comparatively stout pellucid 

 basal membrane. It is very irregular and rugged in its structure, 

 throwing up from its base short, stout, conical masses of spicula 

 terminating acutely and giving a strongly spinous and uneven ap- 

 pearance to the distal surface. I examined the Sponge through this 

 surface, both as an opake and a transparent object, with a power of 

 160 linear, in search of ovaria, but in vain ; but on reversing one of 

 the fragments removed from the leaf, I succeeded in detecting a few 

 very minute immature ovaries closely seated on the inner surface of 

 the basal membrane, and completely buried beneath the reticulations 

 of the skeleton. On examining these by nitric acid, I found that 

 none of the spicula of the walls of the ovarium that might be ex- 

 pected to be present were developed ; but a renewed investigation 

 of the whole of the fragments I possessed produced one adult ovary, 

 gL of an inch in diameter, which I succeeded in isolating and pre- 

 paring successfully for observation. On immersion in water, and 

 when fully expanded, it appeared of a light cream-colour, with an 

 even but slightly pitted surface, to which a few fusiformi-acerate 

 spicula, very much less than those of the skeleton, and very variable 

 in size, were adherent. After careful preparation of the gemmule in 

 nitric acid, these spicula were found to be entirely spined, but the 

 spines are so minute as to require a power of 660 linear to exhibit 

 them in a satisfactory manner. An average-sized spiculum of this 

 description measured, length y^J-^ inch, greatest diameter -^^ inch. 

 The walls of the ovary were filled with stout inequi-birotulate spi- 

 cula Y^i i^^^ ^^ length ; the larger rotula measured ywf^ i"^*^^ ^^ 

 diameter, and the smaller one yjVh ^"^^^ ^'^ diameter. The shaft is 

 cylindrical, expanding slightly towards each end ; the diameter at 

 the middle was e-jjVir inch. The central canal in the shaft is un- 

 usually and strikingly visible ; and at its terminations in the rotulae 

 it throws off numerous minute radiating branches, extending from 

 the centre to the circumference of those parts of the spiculum, giving 

 to them, when viewed with a linear power of 660, a radially lineated 

 appearance. In one of the large rotulae I counted nineteen of these 

 mii\ute canals. 



