160 HOME STUDIES IN NATURE. 



the valve suddenly opened and engulfed the larva with 

 sufficient force to send it to the opposite side of the 

 utricle. 



Mr. Darwin says the valve does not appear to be in 

 the least irritable, and continues ("Insectivorous Plants," 

 p. 408) : " We may therefore conclude that the animals 

 enter merely by forcing their way through the slit-like 

 orifice, their heads serving as a wedge." But we have 

 seen in the instances of the mosquito and chironomns 

 larvae that this is not the case ; the head does not serve 

 as a wedge. But what is the force that impels them 

 into the utricle? It seems too bad to try to overthrow 

 a plausible theory and offer nothing better in its stead. 

 But what can I do? The play is enacted before me, 

 and I have tried in vain to get behind the scenes to 

 learn what the power is that impels the larva into the 

 utricle. No doubt if Mr. Darwin had had the excel- 

 lent material that I had to work with, with his keener 

 insight he would have ferreted out the cause. 



If within the utricle was a partial vacuum, the sud- 

 den opening of the valve would create sufficient force 

 to carry whatever happened to be in close proximity 

 into the utricle; and this illustrates the movement we 

 see executed. But how could a vacuum be formed ? 



We can see, if the valve is sensitive, that a mosquito 

 larva would be much more likely to be caught tail first, 

 for it is not often still — almost always wriggling — and 

 when the forked tail brushes against the valve it causes 

 it to open, and the force above alluded to carries the 



