14 MICROSCOPICAL OBJECTS FOUND 



analogous to division is the basis of the increase 

 of most cell structures, animal as well as vege- 

 table. The contraction of the lining membrane 

 is also observed, according to Mr. Hassal, in 

 many Confervse. The assumed absence of 

 starch from their interior is shewn by Meyen, 

 Ralfs, and Jenner, to be an error. 



On the other hand, there are certain peculi- 

 arities of a positive kind which identify them with 

 plants. Of these I will only cite that of conju- 

 gation, which connects them by the closest possible 

 analogy, with a large number of true Algae. 



The real nature of the allied group of the 

 Diatomacese is a question less easily disposed of. 

 They are objects more or less filamentous, the 

 filaments being divided into joints or frustules, 

 composed of pure transparent silex, and containing 

 in their interior brown colouring matter, and a 

 number of vertical siliceous plates, the visible 

 edges of which often give to the surface of the 

 frustules the most elaborate markings. These 

 joints exhibit a constant tendency towards a partial 

 separation, cohering only by one of their angles. 

 Their reproduction appears analogous in many 

 cases to that of the Desmidiaceee, being probably 



