Ill 



ITS PERIODIC RETARDATION 



83 



Fig. 13 shews the curve of growth of the silkworm*, during its 

 whole larv 1 hfe, up to the time of its entering the chrysalis stage. 



The silkworm moults four times, at intervals of about a week, 

 the first moult being on the sixth or seventh day after hatching. 

 A distinct retardation of growth is exhibited on our curve in the 

 case of the third and fourth moults ; while a similar retardation 

 accompanies the first and second moults also, but the scale of 

 our diagram does not render it visible. When the worm is about 

 seven weeks old, a remarkable process of "purgation" takes place, 



5 

 Fig. 12. Growth in weight of Mouse. (After W. Ostwald.) 



as a preliminary to entering on the pupal, or chrysaHs, stage; 

 and the great and sudden loss of weight which accompanies this 

 process is the most marked feature of our curve. 



The rate of growth in the tadpole | (Fig. 14) is hkewise marked 

 by epochs of retardation, and finally by a sudden and drastic 

 change. There is a slight diminution in weight immediately after 



* Lupiani e Lo Monaco, Arch. Ital. de Biologie, xxvn, p. 340, 1897. 

 t Schaper, Arch. f. Entwickdmigsmech. xiv, p. 35fi, 1902. Cf. Barfiirth, Ver- 

 suche iiber die Verwandlung der Froschlarven, Arch. f. mikr. Anat. xxix, 1887. 



6—2 



