OBSERVATIONS ON LIVING SPECIMENS. 



9 



sp.?, Orbiculina adunca, and Orbitolites duplex. In all observations 

 a rhythmic movement was noted rather than a steady rate. Table 

 1 gives the rate for a specimen of Iridia diaphana which had left 

 its test. The intervals of time for traveling one-sixth of a milli- 

 meter are for a continued movement which covered 4 mm. 



Table 2 gives the rate of movement of a specimen of Discorbis 

 during a short interval. The distance is again a unit of one-sixth 

 of a millimeter. 



At the end of the period given above, the movement abruptly 

 stopped, and it was found that the pseudopodia had come into 

 contact with those of an Orbiculina in the same dish. Those 

 pseudopodia in contact with Orbiculina gradually were withdrawn 

 and movement was continued nearly at right angles to the previous 

 direction. The test had been broadside down during the first 

 movement, but with the change in direction the test itself was 

 tilted on edge. Table 3 gives the rate of movement of a specimen 

 of Orbiculina adunca during a short interval. The distance is in 

 units of one-sixth of a millimeter. 



Table 4 gives a few time-intervals for a short movement of the 

 test in Orbitolites duplex for unit distances of one-sixth of a millimeter. 



As a rule, it seems that specimens with very slender pseudopodia, 

 such as are developed in Orbiculina and Orbitolites, have a com- 

 paratively slower movement than that in which the pseudopodia 

 are thicker and there is a greater coalescence, as in Iridia. 



In both Orbiculina adunca and Orbitolites duplex the pseudopodia 

 are very slender, there is very little anastomosing, and the branch- 

 ing, when it occurs, is at a very acute angle. In Orbiculina adunca 

 the pseudopodia are put out only from the apertures of the periphery. 

 They are very numerous, and with the constant streaming motion 

 soon bring in various kinds of foreign matter to the apertural border, 

 covering it for some distance with a ring or band of such material. 



In Orbitolites duplex a group of 3 to 12 pseudopodia are thrust 

 out from each aperture. 



