JAPANESE FRESHWATER SPONGES. 



107 



gemmule small, spherical, provided with a thick coating of relatively 

 large polygonal " air-cells " arranged in several or many tiers ; with 

 a single aperture, to which is attached a long, stout foraminal 

 tubercle ; the foraminal tubule projecting outwards from the side and 

 then bending downwards, expanding slightly towards the distal end. 

 Gemmule spicules somewhat scanty, arranged irregularly, sometimes 

 forming two layers, one of which is in contact with the chitinous 

 coat of the gemmule, while the other lies on the external surface 



of the outermost tier of " air-cells ". 

 Measurements : — 



Average length of skeleton spicule 0.2924 mm. 



Greatest diameter of skeleton spicule 0.016 ,, 



Length of gemmule spicule 0.088-0. 1 „ 



Greatest diameter of gemmule spicule 0.004 » 



Diameter of single gemmule (without " air- 

 cells ") 0.272-0.306 „ 



HABITAT : Pond in the grounds of the University of Tokyo, Japan 

 November, 1908. 



The specimens, containing many immature gemmules and having 

 clearly been in a vigorous condition when killed, would suggest that 

 in Japan, as in other temperate climates, gemmules are produced at 

 the approach of winter. In India, on the other hand, gemmules are 

 produced, in most species, mainly at the approach of the hot weather 

 although the winter months are here the driest as well as the coolest. 



One of the specimens has its substance pervaded by the tubes 

 of a Polyzoon of the genus Plumatella, as is often the case as regards 

 freshwater sponges of many species in Europe, Africa and Asia. 



Genus Ephydatia, Lamouroux. 

 Ephydatia semispongilla, sp. nov. (Pl. II, fig. 2). 

 SPONGE forming filmy layers of small extent and generally of a 



