294 



G. P. BIDDER 



cloacal velocity would be multiplied by 4, 5, or 6, as the case 

 might be, to obtain the oscular velocity. A pretty method was 

 arrived at accidentally (Text -fig. 3), when I found the coloured 

 jet marked by dark beads or nodes, caused by my pulse shaking 



Text-fig. 1. 



Leucandra aspera var. gigantea (A. 11).^ 



the pipette ; the length between any two nodes, divided by 

 three-quarters of a second, gives the core-velocity at that part 

 of the jet. 



The fastest oscular velocity recorded directly for the 



1 This sponge came from tlie Porto Militare, and I regret that I have 

 drawn it erect instead of pendent. Vosmaer states that this metamp 

 of L. aspera is found only on the keels of boats (cf. p. 314). 



