No. 501] 



NOTES AND LITERATURE 



621 



The pedicels have not the same importance for locomotion in 

 sea-cucumbers as in sea-urchins and star-fishes. The sea-cucum- 

 ber moves by worm-like contractions of the parts of the body. 

 The pedicels on the part temporarily at rest either suck hold of 

 the solid bottom or burr into the slime, and thus serve to give 

 a firm basis from which the other parts of the body may be 

 extended. Ostergren (1897) proves that the anchor-like spicules 

 of the Synaptidae are locomotor. Even in the pedate holo- 

 thurians, the spicules help to make a firm anchorage for the 

 resting part of the body while the moving part is bent away 

 from the bottom and thus the rough points made by the spicules 

 do not hinder the forward movement. Some sea-cucumbers, 

 like the remarkable Pelagothuria, swim, and in them the pedicels 

 are small and weak. 



On the other hand, the Dendrochirotae, which remain for a 

 long time in one spot, have well-developed pedicels so that they 

 can suck fast to rocks, or algae, or on soft bottom, burrow into 

 the slime and by means of their suckers ballast themselves with 

 stones and fragments of shells. The pedicels often gather weeds 

 and shells which form a protective mask. In holothurians with- 

 out pedicels, the spicules serve for this protective function. In 

 very different groups spicules of the same form, albeit actually 

 fundamentally different, may be developed without indicating 

 any natural relationship of the groups. Such, for instance, are 

 the anchors of the Synaptidae, and the Molpadiidae. The branch- 

 ing of the calcareous rods is always in a manner best adapted 

 to form the spicule with economy of material. 



While admitting that pedicels and tentacles are homologous 

 as external appendages of the ambulacral system, Ostergren 

 claims that they are distinctly different, with no connecting links 

 between, and therefore, like Perrier (1902), declines to follow 

 Ludwig's (1889-92) characterization of the Synaptidae as having 

 tentacle-feet, and no body-feet. On the other hand, he does not 

 follow Perrier in classifying the Molpadiidae as apodous, but 

 considers the anal papillae as reduced pedicels which, like sim- 

 ilar appendages in the Aspidochirota? and Dendrochirotae, have 

 evolved as tactile organs. 



Ludwig (1891) proves for one of the Dendrochirotae, Cucu- 

 uturia phtnci, and the present writer has shown (Edwards, 1889 

 1905) for one of the Aspidochirotae, Holothuria floridana, that 

 the tentacles develop from the radial canals in the same manner 



