PRACTICAL NOTES ON 44 HETEROGENESIS.” 349 
and at h, l , m they are seen to resolve themselves into bacteria 
again ! 
Now, if Dr. Bastian had in this case only watched more con- 
tinuously, and with the care required, he would have found that 
he had here the complete life-cycle of a monad ; and by doing so 
would have handed over a useful fact to science. But as it is, 
the truth is absolutely obscured. 
The facts may be briefly glanced at. A monad life-history, 
in all essential respects agreeing with the 44 heterogenetic ” 
stages just given, was worked out and published in the 
44 Monthly Microscopical Journal.” * It originates in a defi- 
nitely discovered and carefully followed germ. In fig. 1 6 is a 
drawing of a germ arising in the pellicle. This was under a 
magnification of 3,500 diams. ; and in the drawing all is 
reduced to one-fourth, except the germ just commencing to 
develop, which is exaggerated, even at the full magnification, 
for the sake of clearness, and shown at a. Fig. 1 6 2 , a drawing 
made on the same conditions, shows the early development of 
the germ. Fig. 17 is a fully developed monad. After a greater 
or less length of time spent in multiplication by fission, it 
becomes amoeboid , as seen in fig. 18. This may be compared 
with c c c, fig. 15. This amoeboid state becomes very gene- 
ral, and two meet, as at fig. 19, and instantly unite, the blend- 
ing going on until the two forms are united into one, as seen in 
fig. 20, each of which may be compared with d (lower figure), 
fig. 15. Encystment now rapidly ensues, and is in progress at 
fig. 21, which may be put beside d (upper figure), fig. 15 ; 
and this is complete in fig. 22, perfectly comparable to e,/, g , 
fig. 15. This cyst eventually pours out — certainly not bacteria — 
but germs, which were watched continuously into the parent 
form. Thus what Dr. Bastian supposed was the 44 transformation” 
by 44 heterogenesis ” of one vital form into another, was in fact 
only a series of stages in the metamorphosis through which a 
monad with an ascertainable history was passing. While in 
the same journal f another such history is given in which the 
organism, after passing through similar preceding changes, be- 
comes a cyst, which pours out living young . 
Thus, wherever certain knowledge is brought to bear upon 
the reputed cases of 44 heterogenesis,” they are easily shown to 
be erroneous and misleading, and afford no foundation for the 
superstructure that has been raised upon them. As no sound 
philosophy can be opposed to the conception of a continuity in 
Nature, and no true science can object to its discovery, but must 
* u Besearche3 on the Life-History of a Cercomonad.” ByDallinger and 
Drysdale. Vol. x. p. 53. 
t Vol. xi. p. 7. 
