TEN-LEGGED PANTOPODS 101 



This table shows two genera belonging to 

 different families of a comparatively small order, 

 with one very prominent character in common 

 which cannot be referred back to a common 



origin. 



Quite recently a letter from Dr W. T. Caiman, 

 containing further references to Antarctic Panto- 

 poda, appeared in Nature (vol. lxxxiv., 28th July 

 1 9 10, p. 104), which adds to the importance of 

 this case. A third genus of ten-legged Panto- 

 pods, named Pentapycnon by Professor E. L. 

 Bouvier, has been obtained by Dr Charcot's 

 expedition in the Pourquoi Pas, and "strange 

 to say, it appears to be quite unrelated to the 

 other two. Pentapycnon charcoti is a near relative 

 of Pycnogonum, hitherto regarded as the most 

 highly-specialised of all Pycnogonida. Further, 

 just as Pentanymphon is accompanied by a species 

 of Nymphon, and Decolopoda by Colossendeis, so 

 Professor Bouvier finds that Pycnogonum, hitherto 

 unknown from Antarctic seas, is represented by 

 a new species alongside of Pentapycnon at the 

 South Shetlands." 



We may now consider the case of two genera 



of toads belonging to one family (Bufonidae) of 



a large order (Batrachia-Anura). These show 



several exceptional characters in common, side 



by side with a number of strongly divergent 



features. The divergences in structure and 



distribution are so great as to make it doubtful 



G 2 



