222 A MONOGRAPH OF THE 



it to be a Zoophyte, he would have designated it as a 

 Spongia. 



36. Hymeniacidon gelatinosa, Boiverbank. 



Sponge. Coating, thin, gelatinoid. Surface smooth and 

 even. Oscula simple, dispersed. Pores inconspicuous. 

 Dermal membrane aspiculous. Skeleton, consisting 

 of a few long and slender spinulate spicula, usually 

 dispersed on a basal membrane, rarely loosely fas- 

 ciculated. 



Colour. In spirit, dull-green. 



Habitat. Dourie Voe, Shetland, Rev. A. M. Norman. 



Examined. From the spirit. 



There is very little can be said about this species. It is 

 one of the simplest spongeous bodies I have yet seen. It 

 consists of a slightly oval patch, about eight lines in length 

 by six in width, and not exceeding half a line in thickness, 

 on a thin fragment of sand-stone shale, slightly exceeding 

 the sponge in size. In its present condition it closely re- 

 sembles a drop of glue spread out on the small fragment 

 of stone. When viewed by the aid of a lens of an inch focus 

 the surface appears smooth and even, and the oscula, 

 although they are all closed, are apparent, as the distal 

 terminations of the excurrent orifices are distinctly seen 

 through the transparent dermal membrane, which is also 

 slightly depressed over the orifices. When a small portion 

 of the sponge was immersed in distilled water innumerable 

 minute globular vesicles were liberated from the sarcode, 

 which appears to consist nearly entirely of these molecules. 

 Small pieces, of the entire thickness of the sponge, mounted 

 in Canada balsam, exhibited the spicula in situ, but they 

 were so few in number that they were as frequently isolated 

 as they were crossing or touching each other ; they were all 

 long and slender, but very variable in their proportions ; a 

 few were congregated in two loose fasciculi, all their bases 



