THE WONDER OF LIFE 521 



digestive secretion ; more and more glands join in ; and 

 the two blades bulge outwards partly with the fly and 

 partly with the copious digestive juice. It is interesting 

 to notice in passing, as an instance of the unity of physio- 

 logical processes that the closing of the Fly Trap leaf is 

 accompanied by an electrical change similar to that 

 associated with every muscular contraction. 



Snow Shoes. — One might spend a pleasant hfetime in 

 admiring organic adaptations, and even the most matter- 

 of-fact man must admit that many of them are fine examples 

 of attaining effective results by very simple means. Take, 

 for instance, the ' snow shoes ' of the North American 

 Euffed Grouse [Bonasa umbellata). According to Dr. 

 Austin Hobart Clark, these ' snow shoes ' develop in 

 winter as two rows of skin ' scutes ' on each side of each 

 toe, and they increase the area of the foot by as much 

 again. They remind one a httle of the scoUoped margins 

 of the toes in a grebe. Their effect is that the bird is able 

 to tread on the Ughtly-compacted snow without sinking in. 

 It might be interesting to test experimentally whether 

 some artificial stimulus, such as damp ground, would serve 

 to induce the extra integumentary growth at some other 

 season than winter. In regard to the simple mechanism 

 of extra lateral plates, Dr. Clark calls attention to a very 

 interesting point — a quaint structural analogy. A figure 

 of the Ruffed Grouse's toe in winter is very much the same 

 as a figure of the arm of some of the Crinoids or feather- 

 stars from the Deep Sea. Two rows of supplementary 

 plates occur on each side of the median row, and the mean- 

 ing of the adaptation is to increase the receptive surface 

 on which the shower of minute dead organisms is caught. 

 Thus we have convergent adaptation in two creatures almost 



