178 VIGNETTES FROM INVISIBLE LIFE. 



the finest and most delicate precision. In one i.e., 

 AracJuioidiscus Japonicus, in which the valves are of 

 a double nature, the external being horny, and the 

 internal silicious the markings on the external 

 valve are after the pattern of the spider's web 

 (hence its name), and on the internal, like that 

 of a " circular Gothic window," both together 

 forming a remarkable design, executed with mar- 

 vellous delicacy and mathematical exactness. 



Then there are the beautiful Coscinodisccce, with 

 numerous genera and species, not divided into com- 

 partments. In one species (C. ocnlus) the valves 

 are marked with hexagonal areola? or circles, in the 

 centre of which appears a peculiar eye-like forma- 

 tion. Of other discoidal forms, such as Calodiscus, 

 Campylodiscus, Cr asp edo discus, Eupodiscus, Hemi- 

 discus, Hyalodiscus,0dontodiscus, Pododiscus, Stephan- 

 odiscus, with their numerous species and varieties, 

 as well as the immense number of other forms 

 into which the vast realm of the Diatomaceae are 

 divided, we must forbear to speak further. The 

 subject is too vast for such a little work as this, 

 which aims only at awakening an interest in 

 invisible life, and of indicating where or in what 

 direction it may be gratified. 



