6. 



tiian the exhalent siplion, but they are frequently rendered of 

 eqiial length by inj-'ory. Both siphons, figure 14, have betiween 

 their outer and inner layers of epithelium, large bundles of 

 longitudinal muscle fibers, separated by sl\eets of radial muscles. 

 A few circular fibers lie near the epithelium but they are not 

 numerous. Ihe siphons are extended by forcing blood into the 

 spaces holloT/red out in the connective tissue. If the siphon 

 of a young specimen is examined with a moderately high power of 

 the microscope, small, conical papillae mil be seen projecting 

 from its surface, figure 15. Each papilla bears at its tip a 



long, rigid filament. Older specimens show similar papillae, 

 but instead of bearing single elongated filaments, several short- 

 er filaments are borne on the tip of each. Similar papillae are 

 found in vsirious places on the mantle and its modifications. They 

 probably correspond to the "pinselzellen" of FlemmingC^) later 

 described by Dorst^^) and Rawitz i^'^) , 

 Siphonal tentacle and marginal tentacles , - 



The youngest specimen collected with a dredge, shows a 

 little rounded knob, figure 11, st. lying on one side, between 

 the mantle and the siphon. This knob, the rudiment of the si- 

 phonal tentacle, is an outgrowth from the line of imion of the 



