THE WALK OF ARTHROPODS. 679 



from the water, while its hinder abdominal appendages are fixed to 

 the sea-bed, it stretches its legs forwards, those of the same pair 

 acting together, and so draws itself onwards like a caterpillar. This 

 mode of progression is analogous also to what Dixon observed in 

 Tomocerus when using its abdominal sucker. The lobster, Homariis 

 vulgaris, uses its four pairs of legs in walking, according to Demoor, in 

 much the same way as tlie scorpion, Bitfhus, but its limbs act with less 

 mechanical advantage than those of the arachnid. As might be 

 expected, the walk of crabs is irregular and complicated ; the legs of 

 a pair always move alternately, but while the four pairs sometimes 

 follow the rule found in spiders, sometimes the walk is like that ol 

 Biithiis, and at other times the four legs of a side are moved succes- 

 sively and independently. The well-known lateral motion of a crab 

 is caused by the legs of one side acting as tractive levers, while those 

 of the other side push. 



An interesting field for research is before us in the walk of 

 Arthropods, and there can be no doubt that photography will give us 

 more reliable results than any other means which can be used to 

 determine how these creatures use their wonderfully-formed limbs. 



REFERENCES. 



1. Dixon, H. H. — Preliminary Note on the Walking of some of the Arthropoda. 



Sci. Proc. R. Dublin Soc, n s., vol. vii., 1892, pp. 574-8. 



2. Demoor, J. — Recherches sur la Marche des Insectes et des Arachnides. Arch. 



Biol., vol. X., 1890, pp. 567-608, pis. xviii.-xx. 



3. Recherches sur la Marche des Crustaces. Arch. Zool. Exp. etGhi., 2nd 



ser., vol. ix., 1891, pp. 477-502, pis. xix.-xxi. 



4 Graber, Y. — Der Organismus der Insekten. Miinchen, 1877. 



5. Carlet, G. — Sur la Locomotion des Insectes et des Arachnides. Comptes 



Rendus, vol. Ixxxix., 1879, p. 1124. 



6. Morgan, C. Lloyd. — The Beetle in Motion. Nature, vol. xxxv., 1886, p. 7. 



7. Wilkins, A. — The Beetle in Motion. Nature, vol. xxxv., 1887, p. 414. 



8. Carlet, G. — Sur le Mode de Locomotion des Chenilles. Comptes Retidus, vol. 



cvii., 1888, p. 131. 



Geo. H. Carpenter. 



