llS A NURSERY FOR THE MICROSCOPE, 



developing new designs. We give an illustration of 

 the glassy frustule of a British species of Isthmia, 

 magnified four hundred times, to prove that the 



Fig. 75- 



Fig. 74- 



Fig. 76. 



Pinnularia major. Pleurosigma formosum. Navicula didyma. 



application of a higher microscopic power only brings 

 out the beauty of these forms into more prominent 

 relief than otherwise. In this figure the student will 



