The Sponges of Lake Biwa. 5 



in the Arctic Regions and the Tropics, but does not appear to have 



as yet been discovered in Africa or Australia. 



In Japan it is known to us from the following localities :- 

 Lake Noziri, Lake Kizaki and Lake Nakatsuna, Province of 



Shinano. - . 



Lake Biwa and a small lake at Komatsu, Province of Omi. 



A small pond at Yodo near Kyoto. 



Spongilla semisponoiU* (Annandale), nob. comb. nov. 



PI. I, Fig. 4. 



1909, Ephydatia semispongilla, Annandale, Annot. Zool. Jap. VII, p. 107, PL IL fig. 2. 



This species was originally assigned to the genus Ephydatia, 

 but, as its specific name was intended to indicate, actually occupies 

 a position on the border-line between that genus and Spongilla. 

 Its status, in fact, is similar to that of Spongilla (or Ephydatia) 

 crateriformis (Potts), which is assigned by some authors to one and 

 by others to the other of the two genera. On the whole it seems 

 best to confine the name Ephydatia to the species in which the 

 gemmule-spicules have well-defined transverse disks at the ex- 

 tremities. In S. semispongilla the ends of the spicules are irregular- 

 ly swollen and bear a circle, or more usually several consecutive 

 circles, of enlarged spines, but the specialization of this part of the 

 spicule is only a little more highly developed than it is m some 

 specimens of 8. lacustris. We, therefore, propose to transfer the 

 species to the genus Spongilla, in which it should be placed near 

 the type species. 



It is distinguished from S. lacustris not only by the peculiari- 

 ties of its gemmule-spicule but also by the complete absence of free 

 microscleres and by the slenderness of its skeleton-spicules. The 

 last, however, is a character on which, in view of the varieties 

 found in S. lacustris, too much weight must not be placed. The 

 foramen of the gemmule is protected by a curved tubule. 



The colour in life is bright leaf-green. The external form is 

 either that of a very thin film of limited area when growing on the 



1) See Annandale, Faun. Brit. Ind., Fresliw. Sponges, Hydroids & Polyzoa, p. 85 (1911). 



