I06 PALMER : 



of such rifts, but here they are actually demonstrated. In 

 like manner, in apparent ignorance of the work of Smith, and 

 using what is essentially Smith's method, he made more pre- 

 cise our knowledge of what goes on upon the surface of the 

 valve of Pinmdaria. The facts observed by Lauterborn, 

 shorn of mere inference for the present, are briefly these : — 



Moving Pinnularias, when put into India ink emulsion of 

 considerable density, show outside the frustule areas into 

 which the ink particles do not penetrate. In typical instances 

 these areas are of an extent and situation to give the whole 

 diatom, when lying on its girdle, nearly the shape of the 

 figure 8. In this position the silicious frustule itself shows 

 practically as a parallelogram, so that the external substance 

 is seen to be quite deep on each half of the valve, even at 

 times as deep as half the width of the whole cell. This mass 

 of coleoderm, altogether invisible in pure water, is of an 

 apparent firmness in the ink emulsion ; but on attempting to 

 apply a stain, it generally sloughs off into a confused mass 

 upon the slide. * Viewed from the valve side, the moving 

 Phiyitdaria shows a stream of ink particles progressing from 

 the front end backward to the central nodule, such as H. L,. 

 Smith had described. This stream is about as wide as the 

 hyaline area in which the raphe lies, and the ink particles 

 follow the contour of the swelling coleoderm as this is seen in 

 girdle view. On each side of this hyaline area, over the 

 spaces occupied by the costee, the coleoderm seems stationary, 

 and ink particles would not appear to cling to it. 



Arrived at the anterior pore of the central nodule, the ink 

 particles collect into a single stream, which, curving through 

 a little circle in the neighborhood of this central nodule, 

 straightens out again and pushes away toward the rear at an 



*I have had repeated confirmation of this statement; and indeed it 

 is a satisfaction to find Httle to object to in Lauterborn's observations of 

 fact. His apparent belief, however, that the moving Pinnnlaria alwavs 

 shows deep masses of coleoderm, is not in accord with experience, as 

 has been well pointed ont by O. Miiller. 



