ANIMAL NATURE OF JDIATOMEjE. 601 



membrane, or of that internal one which he terms amyla- 

 ceous, and which is the primordial utricle (of azotised 

 quaternary substance) of Mohl. In this second case, 

 there are movements, and cilise by which they are effec- 

 ted. The sporidia of the lower Algae, the spores of the 

 VaucheritB, the spirilla of antheridia, the filaments of 

 Oscillariese, are either destitute of a gelatinous sheath, or 

 it is softened and almost dissolved. The air promotes 

 the development of the gelatinous substance, light and 

 heat that of the amylaceous. 



Inseparable from the preceding question is that of 

 speciological and generic limitations. It is a demon- 

 strated and very important fact, that many organisms 

 described as species and genera of the inferior Algae, are 

 merely transitory forms of more complicated beings. The 

 consequence to be logically deduced, is the exclusion of 

 these supposed species and genera from the catalogue of 

 beings. He who desires to continue the enumeration of 

 them as such, ought, to be consistent with himself, to 

 establish species and genera even of the transitory forms 

 of all other beings in nature, unless he maintain that 

 the transitory forms of inferior organisms differ in this 

 respect from those of the superior, inasmuch as they 

 can persist as such, live, and multiply. I believe that 

 this position cannot be impugned even as respects the 

 most elevated organisms, since Teratology furnishes a 

 sufficient number of examples to prove the possible 

 permanence of every transitory form ; and in the inferior 

 organisms, multiplication is confounded with simple 

 increase. It would remain to be decided whether we 

 could always clearly distinguish reproduction from mul- 

 tipUcation, and if so, whether we possess positive data 

 to determine the attainable point of organic perfection 

 of which every being is capable. But, since we are 

 oftentimes destitute of this secure criterion, we ought to 

 obtain data by observation, and to consider that develop- 

 ment to be the highest which is the highest we are 

 able to observe. Nor can any one assert that if develop- 



