10 PROCEEDINGS OF THE ACADEMY OF [Jan., 



certain bearing on the mode whereby progression is effected. The 

 bending of the body necessarily throws either the anterior or the 

 posterior end of the animal out of the line of progression (figs. 5 

 and 6). The former case (fig. 5) is not inconsistent with Sche- 

 Aviakoff' s views, but the latter is (fig. 6). For such a movement 

 would presumably detach the animal from the gelatinous stalk, yet 

 it is effected with absolutely no pause in the progression. 



Observations made on Echinomera hispida are equally suggestive. 

 Fig. 7a-d shows the several positions successively occupied by a 

 progressing individual of this species in making a turn. It will be 

 seen that the animal bent sharply, so that the axis of the anterior 

 part formed nearly a riglil angle with that of the posterior part. 

 The narrow posterior part then swung rapidly around until it lay in 

 line with the rest of the animal. It seems impossible to avoid the 

 conclusion that this would have resulted in the breaking loose from 

 any attached stalk, with the consequent cessation of progression. 

 Yet there was not the slightest slackening in the speed of the 

 animal, which was considei'able. 



2. On encountering obstructions, gregarines may simply slip off 

 to one side or the other. Frequently, however, when an obstruction 

 is met head-on, the protomerite holds its position for the moment 

 and the animal swings to and fro like a pendulum. There may be 

 one or two to several of these swings, after which the progressive 

 movement may be resumed. This may take place without notice- 

 able change in the shape of the body. 



I am again obliged to differ with Schewiakoff, who (p. 343) 

 says : ' ' Triff t die Gregarine auf ein Hindernis, so steht sie einige 

 Zeil still ; es tritt dann eiue Knickung am Korper der Gregarine 

 auf, worauf die Beweguug in einer neuen, durch die Knickung des 

 Voi-derendes vorgezeichneten Richtung fortgesetzt wird." This 

 may happen, but, according to my observations, more often there is 

 no alteration in the shape of the body. It apparently depends 

 upon the force with which the gregarine strikes the obstruction, this 

 force being not necessarily powerful enough to cause the animal to 

 bend. 



I believe that the swinging to and fro tells strongly against the 

 idea that gregarines are followed by an attached stalk of gelatinous 

 fibres. It is not easy to see how such a swinging could fail to 

 break the animal loose from any such stalk, whereupon it would 



