PLATE I 



EXPLANATION OF riGTJRES 



(For figs. 2, 8 and 9 I am indebted to C. Carlgren of Stockholm; fig. 1 was 

 taken at a show, fig. 7 is a copy after V. Emmel, figs. 3, 4, 5, 6, 10 and 11 

 represent preparations in the Museum of the Biologische Versuchsangstalt, 

 Vienna.) 



1 Bull with pair of extra appendages attached to right shoulder. 



2 Cancer pagurus, chela with pair of extra dactylopodites attached to 

 base of normal dactylopodite. 



3 Alpheus ruber, from below and from above, showing normal Heterochely. 



4 Alpheus dentipes, several of chelae, after autotomy of left big claw, 

 (shown above). 



5 Eriphia vulgaris, normal right-handed individual (above) left-handed 

 individual (below) both seen from below. 



6 Eriphia vulgaris, from below, bearing a pair of supernumerary dactylopo- 

 dites on right chela. 



7 Lobster, normal crusher and nipper claws, from above. 



8 Lobster-claw with pair of extra propodites arising from propodite of a 

 nipper claw. 



9 Analogous case, further developed condition, (the dactylopodite is not 

 photographed in this case). 



10 Lobster with pair of extra dactylopodites at base of the dactylopodite 

 of crusher claw, from above. 



11 Same individual from below. 



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