MOVEMENTS OF ANIMALCULES. 107 



however separate as the upper edges Jipproach, but 

 the form of the mass alters, becoming more lenti- 

 cular, so that when the toothed surfaces are brought 

 into their closest approximation, the outline has a 

 subcircular figure. It is on account of this change 

 of form that I presume the masses themselves to 

 be partially composed of muscle." 



These remarks, although specially made of the 

 Rotifer macrurus^ are in the main applicable to 

 all the Philodinas, but the student must not expect 

 to understand any of the complicated gizzards of 

 the rotifers without repeated observations, and no 

 small exercise of patience. It is common to call 

 the portions of the Philodine-pattern gizzard "stirrup- 

 shaped;" but Mr. Gosse has shewn them to be 

 quadrantic, that is, shaped like the quadrature of 

 a sphere. 



As we are not very well off with subjects for 

 description in these two months, we can afford a 

 little time to consider a question that continually 

 arises in the mind, on viewing the movements of 

 animalcules, and especially of any so highly devel- 

 oped as the rotifers, namely, to what extent motions 

 which appear intelligent, are really the result of 

 anything like a conscious purpose or will. When 

 any of the lower animals — a bee, for example — acts 

 in precisely the same way as all bees have acted 

 since their proceedings have been observed, we settle 



