152 



THE MICROSCOPE. 



Navicula angulata, No. 2, cornered little ship, was first discovered in 

 the Humber; the lines upon its surface resemble the most elegant 



tracery, which are resolva- 

 ble into raised minute dots. 

 The markings are seen to 

 be longitudinal, transverse, 

 and oblique. Man boasts 

 of the fineness and perfec- 

 tion of his handicraft ; his 

 manufacture will be so 

 small that a magnify ing- 

 glass is required to observe 

 it ; he will proudly display 

 a piece of lace of most fra- 

 gile material ; but when he 



fig. 99. 



once gazes through the mi- 



1. Pleurosigma angulatum. 2. Portion of the same, croscope at these objects, 

 magnified 1200 diameters. 3 Portion of P. for- invigible t h j naked 

 mosum magnified 5500 diameters. . J ' 



and sees the perfection of 



Nature's works, he feels abashed, and sinks, conscious of the futility 

 of his attempts to rival the accuracy and completeness given by a 

 guiding power to the most insignificant of its creations. 



The Green Navicula was found by Dr. Mantell in a pool on Clap- 

 ham Common ; it is about the 100th part of an inch in length. In 

 this specimen the ribbed division is distinctly seen, extending the 

 whole length of its shell. 



The Golden Navicula is another beautiful species, and was so named 

 from the numerous points within the shell giving it a bright yellow 

 appearance. The shell is an oblong oval, and has upon it numerous 

 delicate and regular flutings. 



The Eunotia. In this species a furrow is seen the entire length of 

 the shell, from which spring numerous ribs tending towards the edges ; 

 of these, eight maybe counted in the 1200th of an inch; there can 

 also be traced, in the length, a line, by which, when at maturity, the 

 animal divides, and in this manner preserves its generation from age to 

 age. See Plate II. No. 13. 



Siebold says : " I have been unable to detect six openings in the 

 Navicula; and precisely at the spots which Ehrenberg and others 

 suppose they have seen openings, the siliceous cell-membrane becomes 

 thickened, and forms rounded eminences which project internally. On 

 the same two surfaces upon which the thickenings of the siliceous 



