48 Lectures on Bacteria. [^ v. 



develope into Bacteria. The course of the observations, from 

 which this conclusion is drawn, is in most cases not stated 

 with sufficient exactness to allow of our forming a judgment 

 upon them. Still one observation is mentioned which it was 

 admissible and desirable to have repeated and tested. Wigand 

 states, for the removal ' of all doubt about spontaneous forma- 

 tion of Bacteria in the protoplasm of cells,' that motile Bacteria 

 are found in the living healthy cells of the leaf of Trianea bogo- 

 tensis and in those of the hairs of Labiatae. My attention had 

 been directed to the matter from another quarter before I 

 proceeded to examine into this remarkable statement. Trianea 

 is a South American water-plant, which floats in the manner of 

 our Frogbit (Hydrocharis). If living tissue from the fresh 

 healthy leaf is placed under the microscope, we shall really see 

 in many cells the prettiest representations of the appearance of 

 Bacteria, small slender rods, isolated or attached together in 

 short rows and actively following the movements of the proto- 

 plasm and other cell-contents. An excellent representation, as 

 I said, or model. But a drop of dilute muriatic acid destroys 

 the illusion. The acid at once dissolves the rods in Trianea, 

 which it would not do if they were really Bacteria ; they are 

 simply small crystals of calcium oxalate, which often occur in 

 vegetable cells and in the form of rods. Of the same kind are 

 the much less beautiful rods in the young hairs of the leaf of 

 Galeobdolon luteum and Salvia glutinosa, and so also in other 

 Labiatae or lipped-flowered plants. The case is full of instruction, 

 as showing how a preconceived opinion may lead even good and 

 intelligent observers into the greatest absurdities. I should not 

 otherwise have mentioned it, and I do not think it necessary to 

 go any further into similar matters. Such things at all events 

 are not calculated to weaken the proposition, that according to 

 the observations which actually lie before us even the smallest 

 organisms spring only from germs produced from ancestors of 

 the same kind ; and to this we must hold fast in spite of what- 

 ever may be thought possible or desirable. 



