SP ONTAJYEO US- GENERA TION CONTR VERS Y. 453 



dition. Fig. 3 shows the direct genetic product of a third, but this sac 

 did not contain spores, but living young, which swam forth at once 

 upon the bursting of the sac, and by taking in pabulum at all points 

 of the sarcode rapidly grew to the parent size. In Fig. 4 we have 

 new features. The organism is oval, with one flagellum. It multi- 

 plies with enormous rapidity by multiple fission, 1 and then by distinct 

 genetic union a sac is formed and spores emitted ; but they are packed 

 in a glairy fluid, and were so minute that at first our best powers 



failed to reveal them. But they were afterward seen, and their full 

 development traced. In Figs. 5 and 6 we have the same products of 

 the last two monads. In morphological detail they greatly differed 

 from all the preceding ones, and from each other. But the spore-sacs 

 were produced by the same means, and the exquisitely minute spores 

 poured forth were traced through all their stages to the adult condition. 



We have here, then, important indications of fact concerning the 

 nearest allies of the bacteria : they develop from germs. 



We have, besides, the weight of the best experimental evidence 

 pointing clearly to the existence of germs in the bacteria themselves. 

 But the microscope has failed to demonstrate the latter. Its finest 

 powers and finest methods failed to reach them. 



Happily at this juncture Prof. Tyndall has stepped in, and, with 

 his accustomed brilliance and precision, has opened up the path we 

 need. He has presented us with a physical demonstration, of the ex- 

 istence of immeasurably minute molecules of matter utterly beyond 

 the reach of the most powerful combination of lenses yet constructed 

 which are the indispensable precursors of bacteria in sterilized infu- 

 sions^ In short, he has opened up a new and exact method, which 



1 Monthly Microscopical Journal, vol. xi., pp. 69, 70. 



2 Nature, January 27, 1876, p. 252; and February 3, p. 268. 



