ANIMAL NATURE OP DIATOJMEiE. 369 



new inferior individual, and the inferior one of the 

 superior. My observations convince me that the affair 

 does not proceed vsrith so much simplicity. I have 

 often seen the tvpo lateral valves separated, and the 

 intermediate space thus largely amplified. In other 

 cases there appeared only a new inferior valve com- 

 plementary to the superior, the inferior individual thus 

 remaining incomplete. Finally, in others, between 

 the complete superior individual and the incomplete 

 inferior valve, there appeared a new individual, with 

 both its valves ; but nearer together, smaller, finer, with 

 lines much less distinct. The exact exposition of this 

 and other observations relating to it, will form the sub- 

 ject of another Memoir. It may suffice for me to inti- 

 mate here just enough to demonstrate, that in this phe- 

 nomenon there is more complication than that of a 

 simple cellular deduplication {sdoppiamento.) 



The third mode of reproduction discovered by Kiitzing, 

 and that upon which he founds his principal argument 

 in support of the vegetable nature of Diatomese, is com- 

 parable, he says, to the formation of spores or of buds 

 XgemmcB) in plants. The Melosirm consist of globular- 

 shaped individuals united together by means of a fine 

 external siliceous permanent membrane, into a filiform 

 series, in a manner pei'fectly similar to the articulations 

 of a Conferva. Each of these consists of two principal 

 valves, in form like two sections of a sphere or polyhe- 

 dron, inserted upon a cylindrical wall, by means of 

 which the two valves or principal surfaces are united 

 together and continuous. Kiitzing saw some of these 

 presumed articulations to be dilated, as also occurs 

 in those which contain the spores of (Edogonia. 

 Though he observed nothing more, this was suffi- 

 cient for him to declare as a fact the propagation by 

 spores. 



The other fact has reference to those Naviculse which 

 have a simple or multiple sheath, constituted of what 

 he states to be a gelatinous substance consolidated into 



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