120 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



say, until complete sexual maturity. After that period no lost organ or 

 part thereof will be renewed, no matter how long thereafter the spider may 

 live. The function is thus evidently designed to favor the maturity of the 

 species and so insure its continuance. 



Atrophy 

 of Old 



Tissues. 



III. 



As has been said, the regeneration of lost organs is the result of two 

 processes, equally important and interesting, the atrophy of the old tissues 

 and the formation of new. If one cuts off a spider's foot all the 

 tissues which fill up the remainder of the limb disappear, and 

 simultaneously a new organ is originated and completely devel- 

 oped within the cavity of tlie joint from which the old tissues 

 have been atrophied. 



Immediately after the operation Nature begins to cover up the wound, 

 the blood cells form a thick cellular mass, which in the course of three 



days is formed into a 

 hard, dark scab, which 

 serves as a stopple to 

 the open wound. This 

 is shown at Fig. 80, 

 and a longitudinal sec- 

 tion at Fig. 81. In 

 the latter, one sees the 



Fig. 80. 



Flii. 81. 



Forma- 

 tion of 

 Cicatrix 



Fig. 80. View of healed stump of a spider's amputated limb. Fiii, 81. Lon- old CUticlc (ct) United 

 gitudinal section of same; etx, the cicatrix; ct, cuticle; mss, granular .-ii j.i -u A iV, 



mass next the cicatrix; ch.c, chitinized cells; b.c.a, amoeboid blood cells; Wltn Uie SCaD, ailCl 1116 



b.c.r., red blood cells. chitiiious membrane 



under which is the row of deep cells of the matrix (Mtx). Immediately 

 under the surface of the cicatrix lies a mass (mss) of unstratified 

 granular matter, next to which is a nest of cells arranged in 

 rows one above another, gradually diminishing in length and 

 receding into the cavity beneath. Of these the upper tier are 

 "chitinized" cells (ch.c), and the remainder blood cor- 0_ ctx b 



puscles, both red (b.c.r) and amoeboid (b.c.a). The transi- 

 tion or destruction of these cells, and their metamorphosis 

 into the structureless mass of the covering cicatrix, is 

 accomplished gradually. 



Now the matrix, which alone of all the tissues does 

 not undergo entire degeneration, begins to retract little by 



little from the cuticle, thus parting from the ^^^^^^ Ippearanceof 

 cicatrix. It commences at the top of the joint stump when matrix, 



. .,., , • ± 1 Mtx, begins to re- 



within whose cavity its ends are approximated, tract ; a, b, lower and 

 It is withdrawn more and more, forming above upper cavities ; o, ori- 



, flee between them ; 



the old tissues a sort of cupola, to use Wagner s word, cicatrix, ctx. 



Retrac- 

 tion of 

 Matrix. 



