Ill] REGENERATION, OR GROWTH AND REPAIR 149 



curve indicates the time taken to regenerate n per cent, of the 

 amount removed. All the curves converge towards infinity, when 

 the amount removed (as shewn by the ordinate) approaches 75 

 per cent. ; and all of the curves start from zero, for nothing is 

 regenerated where nothing had been removed. Each curve ap- 

 proximates in form to a cubic parabola. 



The amount regenerated varies also with the age of the tadpole 

 and with other factors, such as temperature; in other words, for 

 any given age, or size, of tadpole and also for various, specific 

 temperatures, a similar diagram might be constructed. 



The power of reproducing, or regenerating, a lost hmb is 

 particularly well developed in arthropod animals, and is some- 

 times accompanied by remarkable modification of the form of 

 the regenerated limb. A case in point, which has attracted 

 much attention, occurs in connection with the claws of certain 

 Crustacea*. 



In many Crustacea we have an asymmetry of the great claws, 

 one being larger than the other and also more or less different in 

 form. For instance, in the common lobster, one claw, the larger 

 of the two, is provided with a few great ''crushing" teeth, while 

 the smaller claw has more numerous teeth, small and serrated. 

 Though Aristotle thought otherwise, it appears that the crushing- 

 claw may be on the right or left side, indifferently ; whether it 

 be on one or the other is a problem of "chance." It is otherwise 

 in many other Crustacea, where the larger and more powerful 

 claw is always left or right, as the case may be, according to the 

 species: where, in other words, the "probability" of the large 

 or the small claw being left or being right is tantamount to 

 certainty}". 



The one claw is the larger because it has grown the faster; 



* Cf. Przibram, H., Scheerenumkehr bei dekapoden Crustaceen, Arch. f. Entw. 

 Mech. XIX, 181-247, 1905; xxv, 266-344, 1907. Emmel, ibid, xxii, 542, 1906; 

 Regeneration of lost parts in Lobster, Rep. Comm. Inland Fisheries, Rhode Island, 

 XXXV, xxxvi, 1905-6; Science (n.s.), xxvi, 83-87, 1907. Zeleny, Compensatory 

 Regulation, J. Exp. Zool. n, 1-102, 347-369, 1905; etc. 



t Lobsters are occasionally found with two symmetrical claws : which are then 

 usually serrated, sometimes (but very rai-ely) both blunt-toothed. Cf. Caiman, 

 P.Z.S. 1906, pp. 633, 634, and reff. 



