1887.] NATURAL SCIENCES OF PHILADELPHIA. 191 



This name was at first suggested under the belief that a distinct 

 specific difference existed between the European and the American 

 forms ; an idea that has long since been given up. I now think the 

 resemblance of these forms is quite as close as that of most of those 

 grouped under this name in North America. 

 S. mutica, Potts, Syn. 



This term w'as applied to an ordinary form of S. lacustris during 

 the earlier part of my explorations, before I had learned that it was 

 a very common habit of this species to be without both "crust" and 

 gemmule spicules. 



S. lacustris, var. abortiva, Potts. 



The name abortiva was given to a form of S. lacustris first noticed 

 at Fairmount Dam, Philadelphia, in which careful examination 

 during the summer and autumn months of several years, had failed 

 to discover any gemmules. About the 22nd of November 1883, 

 however, upon again collecting the sponge in its original locality, 

 I found, in one instance, the green sarcode leaving the lines of 

 skeleton spicules and collecting in spots, where, a few days later, 

 were found well defined but immature gemmules, entirely smooth 

 and of a vivid green color; — a feature that lasted all winter. Some 

 fragments in this condition were brought into the house and the 

 warmth of the room was found not merely to retard the completion 

 of the gemmules, but in many cases, to reverse the flow of the 

 amoeboid particles, which l:)egan to reform and rebuild the skeleton 

 frame-work. 



To quote from my note book of that date ; — "The appearance of 

 the sponge as now found, was as if the cells of green sarcode had 

 congested or gathered together 'from their normal position upon 

 the supporting spicules and had just formed immature statoblasts 

 with a very delicate chitinous covering and as yet without either a 

 granular crust or embedded spicules. The skeleton spicules in most 

 cases were entirely bare and the statoblasts bright green." Of another 

 specimen of the same sponge it is remarked. — "This resembled the 

 last mentioned gathering, except that in some places the statoblasts 

 were merely localized by a gradual flowing together of the green 

 sarcode into spots ; and the globular shape and chitinous coat of the 

 gemmules had not yet been attained." 



The whole of this observation has been of great interest to me 

 first, as indicating the necessity of caution in accepting statements, 

 asserting the entire absence of gemmules from sponges collected by 



