1886.] 



NATURAL SCIENCES OF PHILADELPHIA. 



229 



Spicules upon the 



gemmulaj 



abundant, crossing each other 

 upon the crustless, chitinous 

 body. Their shape when 

 smooth is robust -fusiform, 

 with pointed terminations ; 

 the great majority, however, 

 have from one to six or more 

 long spines, non- symmetri- 

 cally placed, but with an 

 evident tendency to group 

 themselves at points about 

 one-fourth the length of the 

 spicule from one or both of 

 its extremities. 



Measurements : Diameter 

 of gemmules 0'036 inches ; 

 skeleton spicules, 0-0068 by 0*0002 inches ; length of average 

 dermal spicule, 0'00066 inches ; of gemmula spicule, 0*00145 

 inches. 



Habitat. Encrusting stones in shallow water. 

 Locality. Lakes or ponds in the vicinity of Heart's Content, 

 Newfoundland ; collected by Mr. A. H. MacKay. 



All the specimens of this sponge came from the neighborhood 

 of Heart's Content, but whether they were gathered from a lake 

 upon the heights or from a brook mentioned by Mr. MacKay near 

 the sea level, does not seem entirely clear. The accompanying 

 illustration (magnified 225 diameters) will suggest the peculiari- 

 ties of its skeleton, dermal and gemmular spiculation. The 

 striking resemblance of the dermal spicules to the minute 

 birotulates, heretofore only known in a corresponding position, 

 in the case of Meyenia evei'etti, will at once impress the student. 

 These are however more variable in size, are occasionally spined, 

 and have their rays more prolonged and more delicately ter- 

 minated. 



It is in the singular character of the spicules surrounding the 

 gemmulae that this sponge must attract peculiar attention. By 

 the system of H, J. Carter, Esq., the fresh-water sponges are 

 now classified into six genera, beside some conditional designa- 

 tions of forms in which the typical features are as yet undis- 

 covered. These six, Spongilla, Meyenia, Heteromeyenia, Tubella, 

 Parmula and Carteriiis, may again be associated into two 

 groups, one of them including only the genus Sj'ongilla, charac- 

 terized by the linear acerate spicules surrounding the gemmulae ; 

 and the other comprising all the other genera, where the spicule 

 of corresponding significance is a hirotulate or some easily recog- 

 nized derivative of that type. Within this latter and larger 

 group intermediate forms, connecting the defined genera, are 

 frequent, and the location of species upon one side or other of 



