EXPLANATION OF PLATE IX 



Fig. I, Lubomirskia baicalensis (Pallas). 



Fig. I. Spicule-fibres dissected out of the external part of the 

 sponge ; photographed by reflected light and magnified by about 

 6 diameters. Fig. la. A fragment of the same dissection stained 

 with pyrogallic acid and viewed by transmitted light ; X 50. 

 c.s.= sheath of spicule-fibre. 



Fig. 2. Baikalospongia intermedia (Dybowski). 



Fig. 2. A hand section (vertical) from the external region of 

 the sponge, showing its compact nature and the absence of a 

 subdermal cavity ; photographed by reflected light and magnified 

 by about 6 diameters. Fig. 2a. Thinner section of the skeleton 

 in the same region ; X 50. e.m. = dermal membrane ; g.l. = 

 growth-line. 



Fig. 3. Baikalospongia bacilli f era (Dybowski). 



Fig. 3. Fragment of the skeleton (unstained) ; X 20. Fig^ 

 3a. Portion of the same stained with pyrogallic acid ; X 100. 

 Fig. 3&. Gemmule, X 20. 



Fig. 4. Fragment of the skeleton of Corvospongilla ultima var. 

 spinosa similarly treated (for comparison) ; X 100. 



Fig. 5. Spicules of Nudospongilla coggini (for comparison 

 with those of B. bacilli/ era) ; X 100. 



