author's abstract of this paper issued 

 by the bibliographic service, mat 23 



THE POWER OF ADHESION IN THE SUCKERS OF 

 OCTOPUS BIMACULATUS VERRILL^ 



G. H. PARKER 



ONE FIGURE 



During the summer months Octopus bimaculatus can be found 

 abundantly in the rocky tidal pools in the neighborhood of the 

 Scripps Institution for Biological Research at La Jolla, California. 

 When this animal is picked up it commonly attaches itself to 

 the hand and fingers of the collector by its suckers, thus producing 

 a strange and almost uncanny sensation. Not only will the whole 

 animal suck to the hand, but an excised arm will exhibit coor- 

 dinated movements and vigorous suction, and even an isolated 

 sucker, w^hen stimulated electrically, will hold to the finger of 

 the experimenter apparently with as much vigor as when it was 

 a portion of the whole animal. These parts, therefore, exhibit a 

 very unusual degree of autonomy and, since the isolated suckers 

 are very conveniently handled, they afford excellent material on 

 which to test the power of suction. 



Freshly excised suckers were suspended by a strong thread to 

 a hanging spring-balance. The sucking disc, which faced down- 

 ward, was then applied to a piece of wet smooth wood and the 

 sucker brought into action by stimulating its base with a faradic 

 current. The electrodes by which the current was applied were 

 manipulated bj^ one hand of the experimenter while by the other 

 hand the piece of wood, to which the sucker had become attached, 

 was lowered till the suction was overcome and the wood and 

 sucker parted. Meanwhile the observer watched the indicator 

 on the spring-balance and noted the point indicated on the scale 

 when the parting occurred. This point gave the breaking force 

 involved and was read in grams. As a rule, four or five such read- 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology at Harvard College. No. 331. 



391 



