MICROSCOPY. 371 



Diatoms in Colored Liquids. 



Professor H. L. Smith states that the communication which 

 exists between the internal protoplasmic substance and the 

 exterior does not take place along the sutures of the connec- 

 tives, but in JVavicula (properly so called) it exists along the 

 raphe, or median line of the valves, and in Surirella and 

 Nitz&chia along the edges of the wings or carina?. The ab- 

 sorption of the indigo, when the diatoms have been left for 

 some days in liquid charged with this substance, is quite ap- 

 parent, and principally at the ends of the median line, near 

 the central nodule. Something similar was seen by Ehren- 

 berg. In a field blue with indigo, the little particles can be 

 seen running along the median line of a large JVavicida (Pin- 

 nularia) on that half of the valve which is in the direction of 

 the forward motion of the diatom; these particles accumu- 

 late at the end of the raphe, near the central nodule, where, in 

 the large Pinnidariece, a minute dot may be discerned, form- 

 ing there a ball, which rotates precisely as though encounter- 

 ing a little stream of liquid issuing at this point. When the 

 motion of the diatom is reversed, the particles traverse along 

 the raphe of the other half of the valve to the centre, form- 

 ing there a ball as before; these balls, after acquiring a cer- 

 tain size, are ruptured, and the particles stream off precisely 

 as though moved by the cilia of a rotifer. There appears to 

 be a gelatinous external hyaline envelope, the presence of 

 which is not only demonstrated by the indigo particles, but 

 by its becoming rapidly colored or stained by a weak solu- 

 tion of fuchsine {Bulletin de la Societe Beige de Microscopie, 

 Nov., 1877). 



Isthmia Nervosa : a Study of its Modes of Growth and Repro- 

 duction. 



Two very interesting papers upon this subject have been 

 published in the May and June numbers of the American 

 Journal of Microscopy ', by the Hon. J. D. Cox, United States 

 Senator, and they show how much can be accomplished by 

 patient working and study of even imperfect materials. To 

 study growth and reproduction one would suppose that liv- 

 ing forms would be necessarv ; vet Senator Cox has arrived 

 at many facts quite valuable by using only the dried or pre- 



