ADHESION AND SPINNING 



415 



plate of tough, rigid material, homologous in its structure and mode 

 of origin to the fish scale. The folds each have for a central body a 

 ridge of connective tissue, in the center of which are wide, spine-like 

 projections that arise by a joint from the bed-plate and extend almost 

 to the edge of the fold. Here they turn toward the upper surface of the 

 fold, and frequently cut through the epithelium and project freely. The 

 bed-plate consists of a number of jointed parts, and is backed by a mus- 

 cular mass on the skull. Different branches of these muscles operate 

 to raise the ridges and elevate the edge of the whole pad. The Remora 



spn. 



FIG. 376. Longitudinal, vertical section through a small region of the grasping organ on the 

 head of a teleost fish, Remora. One of the plates is shown and can be seen to be a modified 

 fin ray. spn., jointed spine; car., cartilaginous base of organ. X 80. 



applies its pad to the side of a shark, a swordfish, or a whale, and the 

 muscles cause a rather weak suction to take place. The greatest suc- 

 tion occurs when the fish is drawn backward, as by the motion of its 

 host, or otherwise. The projecting plates then tend to rise and thus 

 create a vacuum under the pad which is made to adhere the firmer. 



The feet of the insects show some notable examples of temporary 

 adhesion by means of a gummy secretion. In the pine weevil, Hylobius, 

 the entire sole of the foot is crowded by a great mass of the so-called 

 "tenent hairs" which are single hypodermal cells whose bodies remain 

 in the foot, and whose distal ends are produced into long, soft-walled pro- 



