16 PROCEEDINGS OF THE ACADEMY OF [Jan. 



the common movement of a lateral displacement of the protomerite, 

 or a bending jnst behind the septum, it can be seen Avith moderate 

 powers that a wave of disturbance passes down the upper surface 

 well to the rear end of the animal. Under high powers, with their 

 limited focal depth, this wave is not readily seen unless it is the 

 upper surface of the animal that is being watched. It is a very 

 common phenomenon, and it establishes the fact that those muscu- 

 lar impulses which are most evident in the anterior part of the body 

 make their influence felt nearly as far as the posterior extremity. 

 Under moderate powers, it appears only as a wave passing down the 

 upper surface, but if higher powers be used, it can be seen that 

 this wave is the same as the transverse movement described above. 

 That is, bending of the anterior part of the body causes a trans- 

 verse movement of the cuticular striations and superficial granules. 

 Moreover, the character of the bending bears a direct relation to 

 the character of the transverse movement. When the bending is 

 rapid and extensive, so also is the transverse movement, and it is 

 under such circumstances that evident rotation may take place. 



These phenomena are well seen in those animals which are entan- 

 gled in some sticky elastic substance, as described on pp. 12 and 

 13, and shown in fig. 12. Such animals show frequently a more 

 or less continuous bending of the anterior part of the body, and 

 simultaneously the ti-ansverse movement. 



In the case of animals Avhich are gliding freely, the transverse 

 movement is always much less extensive. With these it usually 

 requires an oil-immersion lens to make satisfactory observations, 

 with the result that it is altogether impossible, on account of the large 

 size of Stenophora, to keep enough of the animal under observation 

 at any one time to see if both the bending and the transverse move- 

 ment take place together. Since, however, it is easy to see that an 

 extensive bending is accompanied by an extensive transverse move- 

 ment, it is supposable, by analogy, that the slight transverse move- 

 ment is accompanied by slight bending. 



I was able to obtain a certain amount of evidence that this is so. 

 Observations were made on the protomerite of gliding gregarines, 

 vnth the result of detecting frequent lateral displacements of this 

 part of the animal. These movements were mostly so slight iu 

 extent that it required steady Avatching to detect them, and they 

 would never be noticed with low or medium powers. They occur 



