SP ONTANEO US- GENERA TION CONTR VERS Y. 46 1 



than the " uniflagellate monad," which is the fourth in the series 

 whose life-histories were studied by Dr. Drysdale and myself. 1 Figs. 



7 and 8 will help to make this clear, where Fig. 7 is an exact ren- 

 dering of Dr. Bastian's monad magnified 800 diameters ; and Fig. 



8 is a drawing of the " uniflagellate monad " described by my col- 



Fig. 7. Fig. 8. 



Fig. 7, a Monad found by Dr. Bastian in an infusion after heating up to 275 Fahr., said to 

 be spontaneously generated. 



Fig. 8, the same Monad as seen by Dallinger and Drysdale, and the spore of which (Fig. 4) 

 survives 300 Fahr. 



league and myself, magnified 2,500 diameters. We describe it thus : 

 " Its exterior form is extremely simple, being ovoid, with a sin- 

 gle flagellum. Its long diameter never exceeds the ^qVo P ar ^ of 

 an inch " in length. 2 Now, from a very prolonged and careful study 

 of these organisms, I am convinced that Dr. Bastian's form and ours 

 are absolutely identical. But to make the thing simply irresistible 

 we have further and final evidence. One of the metamorphoses of 

 this monad on its passage to multiple fission is that it loses its flagel- 

 lum, and becomes precisely what Dr. Bastian saw all around a mo- 

 tionless spherule. 3 These little bodies are less in diameter than the 

 active monad, and of precisely the same structure. The identity is 

 thus complete. The evidence is as full as may be ; the monad Dr. 

 Bastian saw was the one whose life-history was fully worked out. As 

 usual, it multiplies by fission, but the fission is multiple. It then 

 passes to a sac-like condition, resulting from the uniting together or 

 fusion of two individuals. This sac becomes still and bursts, as seen 

 in Fig. 4, pouring out spores that taxed our highest powers and closest 

 watching. The spores of only two of the monads studied survived 

 after exposure to a temperature of 300 Fahr. This is one of them. 



Now, Dr. Bastian says, " A drop of the fluid containing several 

 of these active monads was placed for about five minutes on a glass 

 slip in a water-oven, maintained at a temperature of 140 Fahr. All 

 the movements of the monads ceased from that time, and they never 

 afterward showed any signs of life." 4 This is precisely our experi- 

 ence. But now mark the reasoning. This monad was killed at 140 

 Fahr., but it was found in an infusion that had been heated up to 275 

 Fahr. ; therefore it must have originated de novo. 



1 Monthly Microscopical Journal, vol. xi., p. 69, et seq. 2 P. 69, ibid. 



3 P. 69, ibid. 4 " Evolution and the Origin of Life," p. 179. 



