2 Art. 1. — N. Ànnartdale and T. Kawamura : 



A. Free microscleres present in the dermal membrane. 



i. Gemmule-spicules present; gemmules not enclosed 



in special cages of skeleton-spicules. ...S. lacustris. 



ii. No gemmule-spicules; each gemmule enclosed in 



cage of skeleton-spicules S. aspinosa. 



B. No free microscleres. 



i. Coating of air-cells on gemmule granular in ap- 

 pearance. 



a. Gemmule-spicules abundant, semi-erect, swol- 

 len at the extremities, which bear circles of 

 enlarged spines; skeleton-spicules very slender. 



S. semispongilla. 



1). Gemmules often absent; their spicules scanty, 

 horizontal, tapering at the extremities, with- 

 out enlarged spines; skeleton-spicules rather 



stout S. dementis. 



ii. Coating of air-cells on gemmule resembling a 

 honeycomb; gemmule-spicules cylindrical or sub- 

 cylindrical, covered with small spines S. fragilis. 



II. Gemmule-spicules with transverse disks at the extremities. 



A. Gemmule-spicules homogeneous, at least subequal, 

 (the margin of their disks serrated, similar at the two 



extremities) [Genus Ephydatia] . 



i. (Shaft of gemmule-spicule hardly longer than the 



diameter of a terminal disk); skeleton-spicules 



smooth or almost so. ...JE. m'ùllevi var. japonica. 



ii. (Shaft of gemmule-spicule similar); middle part of 



skeleton-spicule spiny or granular 



E. m'ùlleri (typical form). 



B. Gemmule-spicules of two distinct kinds, one consider- 

 ably longer than the other. ...[genus Heteromeynia]. 



(skeleton-spicules smooth or with scattered spines; 

 gemmule-spicules not highly differentiated; foramen 

 of gemmule armed with a simple tube without 

 filamentous processes H. hawamurae. 



