52 The Microscope. 



stances at the same degi'ee of temperature." Thus sodium can 

 absorb by its own vapors, that same yellow light when present in 

 the sun, by passing through in the chromosphere and assume a dark 

 line to our spectral vision. 



A NEW FRESHWATER SPONGE. 



HETEKOMEYENIA KADIOSPICULATA N. SP. 

 BY HENRY MILLS. . 



WPONGE massive; specimen 3x2|^ x 2 inches in thickness; tex- 

 ture close, compact; surface nodular; statoblasts, or gemmulae, 

 uniformly globular; diameter, .02 parts of an inch; crust thick, 

 charged with two distinct forms of birotulate spicula; the inner ends 

 of both resting on the chitinous coat of the statoblast. 



Foramenal opening small, slightly prolonged; not funnel- 

 shaped. 



Skeleton spicula generally smooth, a few sparsely microspined; 

 ciirved, moderately sharp pointed; length varying from .012 to .014 

 parts of an inch; long birotulates vary in length from .007 to .009 

 parts of an inch. From thu-ty to sixty of these project irregularly 

 from each statoblast, reaching out beyond the shorter birotulates, one- 

 fourth or more the diameter of the statoblast, and terminating in 

 rotulse, consisting of numerous strong recurved hooks, some of which 

 are turned inward pointing directly to the shaft. Shaft more or less 

 spined, slightly curved, larger in the middle: width of rotulye, .0012. 

 Shorter birotulates large, symmetrical, with irregularly dentate 

 rotulse; rotulae boletiform; shafts straight, strongly ^pined, spines 

 at right angles to shaft tapering to a point. 



Length of short birotulate, .003 inches. Width of rotulse, .001. 

 Dermal, or flesh spicula numerous throughout, small, hexradiate- 

 stellate; with rays or arms of various extent proceeding in all direc- 

 tions from a common center ; center without form or other character, 

 except that which is incident to the junction of the many spines 

 which make up the spiculum. Average extent of stellate spicula 

 measured from the ends of opposite rays, .001. Rays sometimes of 

 uniform thickness, occasionally enlarged at the ends with micro- 

 spines, curved inward. 



There are also manj'- small spicula with one or two long arms, 

 forming an axis from which proceed other i-ays or arms perpendi- 

 cular to the axial rays. These are all microspined, sometimes with 

 blunt terminus, and sometimes tapering slightly. 



