1883.] 



MICROSCOPICAL JOURNAL. 



211 



nitens. This last-named species has 

 the pyramidal columns in the outer 

 crust, like ^. Carteri, all other species 

 having the granular or micro-cellular 

 structure. 



The next genus is Jilc-ycnia, after 

 Meyen, who first discovered the pres- 

 ence of bl-rotulate spicules character- 

 istic of this genus, and it comprises 

 eight species. The statoblasts are 

 globular or oval, the micro-cellular 

 structure of the crust being charged 

 with bi-rotulate spicules, that is, spi- 

 cules which consist of a straight shaft 

 terminated at each end by a disk, even 

 or denticulated at the margin, arranged 

 perpendicularly around the chitinous 

 coat, so that one disk is applied to 

 the latter, while the other forms part 

 of the surface of the statoblast. 



In Mcy:7iia fluviatilis {SpongiUa 

 fluviatilis of Bowerbank), the species 

 most generally known, and in which 

 many varieties occur, as instanced in 

 Mr. Waller's paper on that subject,* 

 the umbonnte disks are deeply and ir- 

 regularly denticulated, and the shafts 

 in some cases more or less spiniferous. 

 The Bombay species, 6". Meyeni, and 

 the river Exe species, 6'. Farjittii, have 

 both kinds of spicules, viz., smooth 

 and spined, proving that they are only 

 varieties of M. fluviatilis. 



In Mcy Cilia phunosa (perhaps the 

 most beautiful of any of the fresh-water 

 sponges as a microscopical object), 

 the statoblasts are oval, with the aper- 

 ture lateral, the umbonate disk is of 

 equal size and the margin is irregu- 

 larly denticulated, with the processes 

 more or less turned inwards. The 

 shaft, is long, straight, and sparsely 

 spiniferous, the spines being large, 

 conical, and perpendicular on their 

 surface. I may mention here, that it 

 is the only species of fresh-water 

 sponge that has the flesh spicule stelli- 

 form, consisting of a number of arms 

 of various lengths radiating from a 

 smooth, globular body, the arms 

 spined throughout. This species 

 comes from Bombay. 



*"Q. M. J,"Vol. V. p. 53. 



The remaining six species are, M. 

 rntiacciis, M. Lcidii, M. gregaria, M. 

 Capewelli^ M. Bai/tyi, and AI. ammyma. 



We now come to the genus 'Jubclia, 

 signifying a little straight trumpet, so 

 named on account of the spicules 

 charging the crust of the statoblast, 

 having the shaft passing, by a trumpet- 

 like expansion, into a disk at one end, 

 this disk being larger than the other. 



The statoblast of this genus is either 

 globular or elliptical, the aperture 

 lateral or terminal. It comprises four 

 species, Tubella reticulata., T. paulata, 

 T. spifiata, and T. recurvata. The 

 typifcal species, T. reticulata., has the 

 slatoblast elliptical, ovoid, aperture 

 terminal, crust composed of micro- 

 cellular substance charged with inequi- 

 bi-rotulate spicules, consisting of a 

 straight shaft passing by a trumpet- 

 like expansion into the larger disk, 

 with two or more spines about the 

 centre, and furnished with a ring-like 

 inflation towards the disk, which disk 

 is circular, smooth, with an even mar- 

 gin, somewhat recurved, the opposite 

 end of the spicule consisting of a cir- 

 cular umbonate head, regularly den- 

 ticulated on the margin, with six or 

 eight conical processes. The spicules 

 are arranged perpendicularly, so that 

 the small end forms part of the surface 

 of the statoblast, whilst the disk rests 

 on the chitinous coat. It is in this 

 genus that the statoblasts seem to 

 have been developed in a capsular 

 covering composed of spicules similar 

 to those forming the skeleton of the 

 sponge, which are bent, subfusiform, 

 and rounded at the ends, only half the 

 size and more thickly spined. This 

 species comes from the river Amazon. 



The remaining genus of which we 

 know anything of the statoblast, is 

 named Partnula, a little round shield, 

 on account of the form of some of 

 the spicules. There are two species, 

 P. Batesii and P. Browiiii. Taking 

 Parmula Batesii as the typical spe- 

 cies, we shall see that the statoblast, 

 besides being a beautiful object when 

 magnified, is very curious in the ar- 

 rangement of its spicules. It is large, 



