188 BIOLOGY FOR BEGINNERS 



The lime is replaced in the new and larger armor and Richard is 

 himself again. Usually the later moults take place in hidden 

 locations and with haste, as the animal is totally helpless and a 

 prey to all sorts of enemies when growing its new suit. It is at this 

 time that " soft shell crabs " are caught, which are merely the 

 ordinary crab in the act of moulting. 



Reproduction of Lost Parts. In moulting or in battle with 

 enemies, it often happens that appendages are lost or injured, in 

 which case the limb is voluntarily shed between its second and 

 third segments. A double membrane prevents much loss of blood, 

 and a whole new appendage is developed to replace the injured 

 member. This accounts for the common sight of crayfish, etc., 

 with one claw much smaller tha"n its mate. 



This reproduction of lost parts depends upon the degree of com- 

 plexity of the part. The earthworm may be able to regrow the 

 whole posterior of its body while a starfish can develop all its or- 

 gans if one ray and its base be left. The hydra and corals nor- 

 mally reproduce by budding off new individuals and the protozoa, 

 simplest of all, regularly reproduce the whole animal by division 

 in two parts. On the other hand, higher forms, such as man, have 

 tissues so highly specialized that we cannot even grow a new 

 finger. The best we can do, is to develop scar tissue to fill a wound, 

 or grow new hair, nails, skin, and (once only) teeth. This is one 

 penalty for high specialization. 



COLLATERAL READING 

 (Crayfish and Lobster) 



N Y. State Forest, Fish and Game Report (1898), p. 290; U. S. Fish 

 Commission Report (1898), p. 229; Invertebrate Morphology, McMur- 

 rich, p. 377; Advanced Text, Claus and Sedgwick, p. 461; Invertebrate 

 Anatomy, Huxley, pp. 265-293; Advanced Text, Parker and Haswell 

 (Vol. I), pp. 498-514; Advanced Text, Packard, pp. 226-272; Animal 

 Forms, Jordan and Kellogg, pp. 93-104; Animal Studies, Jordan, Kel- 

 logg and Heath, pp. 109-120; Animal Activities, French, pp. 101-114; 

 Elementary Text (Zoology}, Kellogg, pp. 144-155; Elementary Text (Zo- 

 ology), Colton, pp. 61-86; Elementary Text (Zoology), Linville and Kelly, 

 pp. 125-156; Elementary Text (Zoology), Morse, pp. 130-147; Elementary 

 Text (Zoology), Needham, pp. 111-129; Elementary Text (Zoology), Daven- 



