MIGRATION. 235 



sistently away from land with the view to reaching the 

 opposite shore, till they succumb to fatigue and the waves. 

 Therefore, pending further observations on the question of 

 fact above alluded to, I cannot feel that the migration of the 

 lemming furnishes any difficulty to the theory of evolution 

 over and above that which is furnished by the larger and 

 more important case of migration in general, to the considera- 

 tion of which I shall now proceed. 



Migration. 



Taking the animal kingdom from below upwards, the first 

 animals that can properly be said to present the instincts of 

 migration are to be found in the group Articulata. I think it 

 is sufficient to refer to " Animal Intelligence " for the facts 

 concerning the migrations of Crabs (pp. 231-2)* and Cater- 

 pillars (238-40), though as regards the latter I may add the 

 following remarkable account, which I quote from the 

 " Colonies and India." 



" To say that a train had been stopped by caterpillars 

 would sound like a Yankee yarn, yet such a thing (according 

 to the " Rangitikei Advocate") actually took place on the 

 local railway a few days ago. In the neighbourhood of Tura- 

 kina, New Zealand, an army of caterpillars, hundreds of 

 thousands strong, was marching across the line, bound for a 

 new field of oats, when the train came along. Thousands of 

 the creeping vermin were crushed by the wheels of the 

 engine, and suddenly the train came to a dead stop. On 

 examination it was found that the wheels of the engine had 

 become so greasy that they kept on revolving without ad- 

 vancing — they could not grip the rails. The guard and the 

 engine-driver procured sand and strewed it on the rails, and 

 the train made a fresh start, hut it was found that during the 

 stoppage caterpillars in thousands had crawled all over tho 

 engine, and over all the carriages inside and out." 



With regard to Butterflies many instances of large migra- 

 tions are mi record. Thus, Madame de Meuron Wolff describes * 

 an immense swarm of the Painted Lady butterfly passing 

 over Grandson, Canton d<' Vaud, Hying closely together from 

 mil to north. The column, which was from ten to fifteen 

 feet broad, flew low and equally, and took two hours to pass. 



• See a ■ Mcjsilcy, A Waturalist on the Challenger, p, fit'!. 



I : 



