98 



PROBLEMS OF RELATIVE GROWTH 



distribution of growth-potential in the three planes of space. 

 The minor differences, e.g. number and form of ' teeth ' are 

 presumably due to specific gene-differences, not correlated 

 directly with growth. 



A further point of interest was elicited in these chelae by 



making measurements not 

 only of whole segments, but 

 to intermediate points marked 

 by spines, etc. (notably the 

 four large spines on the median 

 side of the propus). These 

 measurements indicate that, 

 as suspected, the growth-co- 

 efficient of a given whole seg- 

 ment merely represents a 

 mean value, the growth- 

 gradient being real and con- 

 tinuous, and that the values 

 of the growth-coefficients are 

 altering continuously and 

 regularly along the segment. 

 Many more measurements, 

 however, would be necessary 

 before the true gradients could 

 be plotted in detail, and to 

 obtain these would be a very 

 difficult task, as fixed points 

 to measure are not numerous 

 enough. (See also Locket, p. 

 261.) 



Tucker (1930) has made 

 measurements on the chela of 

 the anomuran Upogebia lit- 

 toralis, for normal specimens 

 of both sexes as well as for 

 those parasitically castrated 

 by the Bopyrid Gyge branch- 

 ialis. The length measure- 

 ment chosen was (propus -f dactylus) while the breadth measure- 

 ment was propus-breadth. The results for normal specimens are 

 shown in Fig. 55. For both males and females, two distinct 

 phases of growth are found, the alteration occurring at 12-13 

 mm. carapace length. In the first phase of both sexes there is 



6 8 10 13 16 19 



carapace length, mm. 



Fig. 55. — Upogebia littoralis (Deca- 

 poda, Reptantia, Anomara). Chela 

 (dactylus + propus) length and chela 

 (propus) breadth against carapace 

 length ; logarithmic plotting. Ste 

 Table XI. 



X , males ; 0, females; .parasitized 



males ; , parasitized females. The male 



chela, as in Uca, begins by being distinctly 

 heterogonic and then becomes less heterogenic. 

 For details, see text. 



(From data of Tucker, 1930.) 



