200 PROCEEDINGS OF THE ACADEMY OF [1887. 



fluviatilis, then only known to me, the sponge to which they belonged 

 was. not unreasonably perhaps, supposed to be new, and the name 

 Spongilla morgiana was suggested for it, (Proc. Acad. Nat. Sci. July 

 1880) from a fanciful resemblance of the gemmules Avith their up- 

 right foramina, to the jars in which the "Forty Thieves" were so 

 neatly "done in oils" by that consummate artist. On coming to a 

 knowledge of Dr. Leidy's description some months later, I sought 

 and found this sponge in his (Dr. L's) original localities. Kepeated 

 comparison of the sponge with the above description resulted in 

 the conviction of their entire agreement, if we regard the author as 

 examining a mass of sessile gemmules after the skeleton spicules had 

 been generally removed. At last a small stone was discovered in 

 in the museum of the Philadelphia Academy, to which was attached 

 the legend, in the author's handwriting, "S. fragilis presented by 

 J. Leidy," and still bearing a few gemmules and spicules of the 

 same species. The identification was then complete, and S. lordii, 

 Bk. 1863 ; S. ottawaensis, Dawson, 1875 ; and S. morgiana, Potts 

 1880, became synonyms. 



Next to S. lacustris, Spongilla fragilis is the most widely distrib- 

 uted American species ; having been found in most of the United 

 States and in all varieties of situations. It seems to grow indif- 

 ferently, in rapidly flowing streams, in currentless reservoirs, and even 

 in nearly stagnant pools. Where it is found at all, the specimens 

 are usually abundant. Upon one occasion when the water was with- 

 drawn from the canal basin at the head of the locks at Fairmount 

 Dam, Philadelphia, the exposed, perpendicular walls of dressed 

 stone were seen to be lined with them, probably hundreds in num- 

 ber; some of minute size, but many covering two or three square feet 

 of surface. They were rarely much more than an inch thick near 

 the middle and shaded off all around to filmy edges. They had no 

 apparent i^reference for the comparatively rough surface of the stones, 

 for some of the finest specimens were found upon the timbers of the 

 gates, from which they were easily removed. 



The large size of the efferent osteoles in this species is a conspic- 

 uous feature ; and within each of them can be seen the terminations 

 of five or six of the larger canals. When mature, say in August or 

 later, the pavement layer of gemmules may generally be found at 

 the base of such specimens ; and in those still older, the segregate 

 or grouped forms are frequently abundant in the higher parts of the 

 sponge. 



