190 PROCEEDINGS OF THE ACADEMY OF [1887. 



possible diminution of the water way and contamination of the drink- 

 ing water by its furtlier growth. 



I have not had an opportunity to examine the type specimen from 

 which the above description by Dr. Bowerbank was prepared, but 

 from the study of fragments received from Mr. Desmond Fitz- 

 Gerald, Chief Engineer of the Boston Water Department, collected 

 by him from Farm Pond and Cochituate Reservoir, near the head of 

 the water system of that city (in all probability tlie same that Di-. 

 Bowerbank describes), I am induced to class this as one of the many 

 varieties of *S'. lacustris. In the dry state the sponge is very friable 

 and its dermal surface soon crumbles off, which may in a measure ac- 

 count for the apparent absence of dermal and interstitial spicules 

 from Dr. B's specimens. Mr. H. J. Carter records the finding of 

 acerate, dermal spicules in those received by him from the same local- 

 ity, and I have found them, though few in number, in the fragments 

 sent to me. We may regard, therefore, the dermal and interstitial 

 surfaces of S. paupereula as not aspiculous and assert that those 

 found are not entirely smooth ; as in nearly all a few spines may be 

 discovered, particularly near the extremities. 



* The gemmule spicules are equally scarce and without pronounced 

 character ; their relative smoothness and greater proportionate length 

 than in most other forms of this species are the noteworthy points. 

 The gemmules are quite numerous, large and entirely devoid of 

 "crust." Their shrunken contents, appearing through the transparent, 

 crustless chitin, give them a peculiar waxen cast. It will be noted, 

 as has before been incidentally inentioned, that in this, as in other 



cases, a paucity of gemmule spicules attends, as a necessary conse- 

 quence, the absence of an envelojiing crust. 



S. lacustris, var. dawsoni, Bowerbank. Proo. Zool. Soe. London 186.'! pg. 467. 



"Sponge sessile, branching ; surface smooth. Oscula and pores 

 inconspicuous. Dermal and interstitial membranes abundantly 

 spiculous ; spicula fusiform-acerate, entirely spined ; spines numer- 

 ous, short and conical. Skeleton spicula acerate or sub-fusiform- 

 acerate. Ovaria spherical ; dermal spicula numerous, disposed in 

 flat fasciculi or groups of spicules parallel to each other (?) ; groups 

 irregularly dispersed ; spicula acerate or sub-cylindrical, entirely 

 spined; spines numerous, obtuse and ill defined. Sarcode aspiculous. 

 <yolor in the dried state emerald green." Bowerbank. 

 S. flexispina, Dawson. Syn. Canadian ISTat. and Geol. Sept. 1875'. 

 iS. lacustrioides, Potts, Syn. 



