630 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXVI. 



Externally the sponge appears to have been bright green in color, but 

 the basal parts are yellowish. The texture is light and friable, by 

 no means elastic. 



In vertical section both radiating and transverse fibers are visible to 

 the naked eye and the sponge has a distinctly reticulate appearance, 

 although the vertical interspaces are much more conspicuous than 

 the horizontal ones. Wide circular canals penetrate the sponge in a 

 course parallel to its base. Comparatively little spongin is present. 

 Under the microscope it is evident that the radiating fibers are much 



more coherent and reg- 



A 



X240. 



ular than the trans- 

 verse ones. On the 

 external surface of the 

 sponge a network of 

 horizontal spicules can 

 be distinguished. 



There is a delicate 

 b a s a 1 structureless 

 membrane. The ecto- 

 dermal membrane has 

 perished. 



The skeleton spicules 

 measure 0.174 mm. to 

 0.278 mm. in length 

 and on an average 

 0.021 mm. in greatest 

 transverse diameter. 

 They are very sharply 

 l)ointed at both ends, 

 straight or nearly so, 

 smooth or somewhat sparsely covered with extremely minute projec- 

 tions, the ends being always smooth. 

 There are no flesh spicules. 



The gemmule spicules are very variable in length, measuring from 

 0.071)8 mm. to 0.122 mm. in length and about 0.0031 mm. in transverse 

 diameter. They are cylindrical, straight or nearly so, armed with 

 somewdiat irregular spines, which are often slightly retroverted at 

 the two ends. 'Sometimes there is a single straight spine at either 

 end, but often the spicule ends abruptly and is surrounded by a ring 

 of spines in such a way as to suggest a rudimentary rotule. 



There are few gemmules, those that exist occurring singly in the 

 substance of the sponge and being free. They have a blackish color, 

 are si^herical, measuring on an average 0.G09 mm. in diameter. Each 

 is provided with a single aperture, to which a short, straight, rather 

 stout foraminal tubule is attached. The inner chitinous coat is 



a 



X240. 



Fig. 3. — Spon'uill.v I'liir-ii'i'ixE.NSis. n, skeleton 



SPICULES ; h, GEMMULE SPICULE. 



