1894.] 3IICI10SC0PICAL JOURNAL. 233 



readily recognized, and followed with a power of x 200, 

 or a 1-2 inch lens, and A eye piece. 



Attentive watching the marginal contact of the gran- 

 ules of carbon in advance of the path passed over will 

 reveal the pseudopodial-like flow (characteristic of the 

 movements of Amoeba proteus ) of the fringe of exoplasm 

 at the advancing end of the diatom frustule. Then it 

 may also be variously noted that the carbon area never 

 comes into direct contact with the siliceous frustule, but 

 seems to be driven, away in advance and blown off to 

 the sides of the diatom. It passes downward in the outer 

 zone, or fringe exoplasm charged with the granules of 

 carbon. If while the attention is thus occupied, and the 

 diatom is seen to back, or take a retrograde movement, 

 it will then be observed, that the end thus previously 

 charged with the pseudopodial flow has become relative- 

 ly passive and draws a long coma, or train of granules 

 of carbon in its path. The current of carbon granules 

 may be traced for considerable distance to the rear of the 

 diatom. The carbon granules flow inward to the axial 

 line of the diatom's motion after it passes any given 

 visible stationary speck on the slide, but while the ex- 

 oplasmic train of the retreating end of the diatom seems 

 to be passive (i. e., not assisting in propulsion.) Yet 

 from time to time, some particles of debris, or other 

 matter may be gathered by it, and hurried into contact 

 with the posterior end of the frustule. If the attention 

 is now again directed to the anterior, or advancing end, 

 the pseudopodial or amoeba-like flow, or advanced undu- 

 lations of the exoplasm will be again noted, as in the in- 

 stance previously given. Should reversal of motion oc- 

 cur, the phenomena are repeated inversely as often as 

 change of direction occurs. 



Next the attention may be directed to the motility of 

 particles of debris, flecks, or cloudlets of carbon driven 

 along the peripheral edges of the frustule. The pseudo- 



