1887.] NATURAL SCIKNCES OF PHILADELPHIA. 1^1) 



sufficient vitality to support themselves above the mud, slowly gatli- 

 ering around them.^ 



While S. lacustris is extremely variable, as to some particulars, 

 upon this continent, (as Prof. Vejdovsky describes it to be also in 

 Europe), in essentials the synonyms I have named resemble one 

 another and the European type. These essentials, for comparison, 

 I again describe as follows : — 



1st. In general appearance, a green, branching sponge. 

 2nd. Skeleton made up of smooth, fasciculated spicules. 

 Ijrd. Dermal or flesh spicules, fusiform acetates, entirely spined, 



pointed. 

 4th. Gemmule spicules, whether few or many, generally cylindri- 

 cal, more or less curved, rather sparsely spined, spines often 

 recurved, acute. 

 5th. Gemmules either apparently wanting or abundant througliont 

 the sponge ; with or without granular crust. 

 As all the sponges above named will bear this description, I can- 

 not see sufficient reason for separating them from the typical form, 

 but many for grouping all together. Some, whose peculiarities are 

 most conspicuous, will be briefly described as varieties. 



S. lacustris, var. paupercula, ISowerbank. Proc. Zool. Soc. Lond. 1861! p. 470. 



"Sponge coating and branching ; surface smooth. Oscula and 

 pores inconspicuous. Dermal menbrane aspiculous (?). Skeleton 

 spicules fusiform-acerate, stout and rather short. Interstitial mem- 

 branes <aspiculous. Ovaries globular, smooth ; spicula acerate, 

 small, few in number." Bowerbank. 



Loc. Water pipes of Boston, Mass. 



S. paupercula, Bk. is, perhaps, that one of this group of synonyms 

 about whose identity with S. lacustris there may be most hesitation. 

 Its character is somewhat anomalous, as its locality and associations 

 are peculiar. (See remarks as to M. fluvi.atilis,v. acuminata.) Grow- 

 ing originally in the ponds and reservoirs tributary to the Boston 

 water-supply, it moved forward, and even so early as 1856 Prof. 

 J. W. Bailey wrote to Dr. Bowerbank that "it grows abundantly in 

 the water pipes (aqueducts ?) by which the city of Bo.ston is sup- 

 plied with water from a small lake"; adding a suggestion as to the 



n'his is thus far the only instance in which I have found any sponge apparently 

 growing upon a mud bottom ; and even here it was doubtless planted upon sonic- 

 thing firmer, and the length of its branches was probably induced by the effort to 

 lift itself up into greater purity and freedom. 



