REGENERATION AND DEATH 207 



the useful applications of which are immediately 

 obvious to every one. 



We find in the process of regeneration of organs 

 or parts of the body that it is always the young cell 

 which plays the principal part. This is beautifully 

 illustrated in the picture upon the screen, Fig. 70. 

 There is a little creature, which many of you have 

 seen in the garden, consisting of joints, which rolls 

 itself up into a little ball, and therefore is often called 

 the " pill-bug." It is not, however, an insect or a bug, 

 properly so-called, but belongs to a family of crusta- 

 ceans. It has on its head a little feeler which we 

 call the antenna. The particular kind of arthropod, 

 the antenna of which has been studied and drawings 

 of it made to furnish us this plate, is known by the 

 name of Oniscus. In his researches the experimenter, 

 Dr. Ost, 1 cut off the antenna in the middle of a joint 

 and found that it rapidly healed over. Here are pic- 

 tured the stages of the progressive restoration. Part 

 of the antenna has been cut off in this case; the wound 

 was healed over here, No. i, a, the new tissue has 

 begun to grow, No. 2, 6, and the cells at this point 

 are very simple in character. They spread out and 

 grow, and then, within the interior of the hard shell of 

 the feeler, a retraction of the substance occurs, and 

 the new growing cells within this space gradually be- 

 gin to shape themselves out, No. 3, b, and we see 

 presently an accumulation of cells which is assuming 



Ost, J., " Zur Kenntniss der Regeneration der Extremitaten bei den Arthro- 

 poden," Archiv f. Ent-urickeluntrsmechanik, xxii., 289-324, pis. x-xii. 



