JAPANESE FRESHWATER SPONGES. 



IOQ 



This sponge resembles some of the species of the subgenus 

 Euspongilla (genus Spoiigilhi) in more than one respect but is 

 clearly an Ephydatia. The feeble development of the rotules of its 

 gemmule spicules is a character which it shares with some forms of 

 Ephydatia crateriformis, a North American species with which the 

 Indian E. indica is probably identical. I have pointed out elsewhere, 

 however, that there is considerable seasonal variation as regards the 

 form of the birotulates in E. indica 1 . 



Ephi/ilatia japonica (Hilgendorf). (Pl. II, fig. 3). 



Spongilla fluviatilis var. japonica, Hilgendorf, S.-B. Gcs. Natur- 

 forsch. Freunde Berlin 1882, p. 26. 



Ephydatia fluviatilis var. japonica, Weltner, Archiv f. Naturgesch. 

 1895, Bd. I, pp. 123, 134. 



This sponge was originally described from Tokyo by Hilgendorf, 

 who regarded it as a variety of Ephydatia flnviatilis. Weltner 

 apparenti}' examined the type, which is in the Berlin collection, and 

 also assigned it to E. flnviatilis. After examining a specimen 

 collected by Dr. Oka in Lake Aoki, Shinano Province, however, I 

 find myself forced to regard the form as distinct species, which may 

 be recognized by its smooth skeleton spicules and short-shafted 

 birotulates with no spines on the shaft but with deeply serrated 

 rotules. The following arc the measurements of the spicules and 

 gemmule in the specimen I have examined, compared with those 

 given by Hilgendorf : — 



Length of skeleton spicule.. 0.238-0.272 mm. — 0.343-0.38 mm. 

 Greatest diameter of skeleton 



(Ililgenclorf) 



spicule 



Length of birotulate 



0.0I2-0.02 



0.01 6' 



,, . — 0.014-0.017 



0.029 



I) Ree. Ind. Mus vol. I, p. 273. 



