The Sponges of Lake Biwa. 27 



Summary. 



I. We have examined specimens of seven species of Spon- 

 gillidae from L. Biwa, of which one {He,teromeyenia kawamurae) 

 is described above as new. 



II. The majority of the species are widely distributed 

 Holarctic forms, but one (Spongitta dementis) is probably of 

 Oriental origin. 



III. The distribution of the species in L. Biwa is correlated 

 with definite differences in environment, and several forms, more 

 particularly S. dementis, differ considerably in different sur- 

 roundings. 



IV. The sponges of L. Biwa attain their full growth as a 

 rule somewhat later in season than those of Europe. The produc- 

 tion of gemmules is also somewhat retarded, but the exact season 

 differs slightly in different species. No form, so far as we are 

 aware, produces gemmules at the beginning of the hot weather. 



V. S. dementis gives shelter on its surface or in its canals to 

 several incolae of different groups, but its precise relation with them 

 are still obscure. It often grows on the shells of several Gastropods 

 and Lamellibranchs and finally overwhelms and probably absorbs 

 the body of the molluscs, the relationship in this case being that 

 of parasite and host. 



Otsu, December 1915. 



Publ. August, 4th. 1916. 



