106 JOURNAL OF THE [October, 



cal deposit of the blue stain had thrown down or coagulated the 

 aniline wherever the blue stain had taken effect. Otherwise, 

 where there were no markings visible on the frustules, as on the 

 smooth median surface divided by the lines of the raphe, 

 there was no stain worth noticing. The raphe was in many 

 cases well differentiated, as well as the two central nodular and 

 two terminal dots of the larger Pinnularice. These two stained 

 slides were the only ones made to test the possibilities and ad- 

 vantages to be derived from staining. As they have given ad- 

 mirable results, it adds another kind of interest in the study of 

 diatoms. Had the material in the slides containing Amphiprora 

 ornata been stained either blue or violet, the Amphiprora therein 

 could have been readily located on the slides, but in the un- 

 dyed state they are extremely hyaline and somewhat difficult 

 to locate in balsam mounts under high powers. 



The two stained slides were prepared for the series illustrat- 

 ing these notes. In connection with these two slides it may be 

 noted that there is little affinity on the superficial surface of the 

 fossil diatoms for the dye, but the external surface of living dia- 

 toms, after drying and mounting, indicates that such surfaces ab- 

 sorb and retain a perceptible amount of dye, which fact suggests 

 that the external layer of protoplasm must have retained it. On 

 an examination of the frustules in the slide stained by the com- 

 pound process, it will be noted that there is an indication of 

 coagula of the dye adherent to the frustules, while this appear- 

 ance is entirely wanting in the Whistler fresh-water living dia- 

 toms as stained with aniline alone, and in the blue-stained fossil 

 diatoms from Montgomery, Ala. 



If my language has been clear, it will be understood that the 

 salient feature of this article is that the diatom is endowed (pos- 

 sibly all diatoms) with two non-interfering motions, qualities in- 

 dicative of life — namely, the direct and retrograde, which is the 

 generally known and universally acknowledged motion of the 

 whole frustule, single, double, or quadruple, and also the sub- 

 jective motility of the exoplasm or protoplasmic covering. The 

 principal characteristics of this latter motion have already been 

 given. This claim is, however, not advanced in the case of the 

 discoidal forms, found adherent by countless thousands to ma- 

 rine algse and the leaves of Valisneria, such as Arachnoidiscus, 



