1887.] NATURAL SCIENCES OF PHILADELPHIA. 267 



flow of this pond made its way to the Schuylkill River through the 

 lovely "Lansdowne Glen," filling the little "Run" that, before and 

 since that summer, has but softly murmured through it, with an un- 

 familiar turmoil of waters. In its normal condition this stream is 

 one a child could step over at almost any point, and all its water 

 could probably be carried through a six-inch pipe. 



That portion of it just below Belmont Avenue has become some- 

 what famous in our local biological annals. It was here that Prof. 

 Leidy found, a year or two after the "Centennial," thousands of col- 

 onies of his beautiful Bryozoan, Cristatella idee, covering every stick 

 and stone. Here in 1878 the writer discovered that frajyraent of 

 Spongilla fragilis, which, thus accidentally, directed his attention 

 toward a line of study in which he has since had such great enjoy- 

 ment ; and here two years later was first found the subject of the 

 present memoir, a sponge whose novelty was exhibited in a greater 

 departure from previously known types, than had been the case with 

 any before discovered. Spongilla tentasj)erma, S. tenosperma, Car- 

 terella tenospenna and Carterms tenosperma, ring the changes in its 

 name and history, till it now stands accepted, I trust, (coincident- 

 ly with C. tubisperma of Mr. Mills,) as the first instance in which 

 the spherical chitinous body of a sponge gemmule has attained a 

 cirrous development, conspicuous in its character and evident in its 

 purpose. 



The cirri in this species are very long and slender; curling and 

 twisting in infinite contortions about themselves and the roots among 

 which they grow; so long, that they have been combed out to an 

 actual length of half an inch, or twenty five times the diameter of 

 the gemmules of which they are parts. More or less of the sponge 

 was found at the same locality for several successive years, until 1885, 

 when, as search was not made until December, its apparent absence 

 was not to be wondered at. 



One circumstance not easily explained must be mentioned as a 

 part of its history. The birotulates of those gemmulre collected in 

 1880 were peculiar in this, there were no proper rotules, and the 

 rays at the ends of each spicule stood out in every direction, like the 

 bristles of a mop. On those gathered during the folloAving, and, so 

 far as I remember, during subsequent years, this habit has changed 

 and the rotules in nearly all cases are perfect. The collections were 

 made at precisely the same locality ; and in all other respects the 

 sponges appear to be identical. 



