PRACTICAL NOTES ON ii HETEROGENESIS. 
341 
on returning to his instrument in the morning, he startled by 
discovering that an anchored springing monad is dotted over the 
“ field,” with perhaps another form swimming freely about. 
Now in this case the inference would he more legitimate than 
in the majority of Dr. Bastian’ s that the bacteria had been 
“ transformed ” into monads. There were the bacteria, alone — 
some of them were seen to enlarge — and here in the course of a 
few hours are vigorous and distinctive monads ! Post hoc , 
projpter hoc. But let this group of monads he now casually 
examined in the same way : in the course of some hours many 
of these will become very still and sac-like ; the crowding of 
the field will increase ; the difficulty of discrimination to inter- 
rupted observation will become greater ; and at the end of 
twelve hours more, some splendid specimens of Kerona pustu- 
lata will he asserting their mastery of the field. Now there is 
no instance presented by Dr. Bastian, as a case of “ transforma- 
tion,” that has a more exact basis to stand upon than is pre- 
sented here for inferring that the bacteria were transformed 
into monads, and that these monads preferred to perpetuate 
existence as Kerona. But what are the facts ? The apparently 
fattening or enlarging bacteria were simply developing monad 
germs, and if continuously watched all the steps from the germ to 
the adult form would have been seen ; and the same continuity of 
observation would have shown that the Kerona had a genetic 
origin as independent of the monads as the monads had of the 
bacteria. Indeed, low in the scale of organisation as the monads 
are, I do not hesitate to affirm that in their development they 
give no sanction or shadow of support to the hypothesis of 
“ heterogenesis.” “ On the contrary, the life-cycle of a monad is 
as rigidly circumscribed within defined limits as that of a mol- 
lusc or a bird. There is no indication of any unusual or more 
intense method of specific mutation than those resulting from 
the secular processes involved in the Darwinian law, which is 
held to furnish the only legitimate theory of the origin of 
species.” * 
But to the young and ardent observer the example set by 
Dr. Bastian might prove the utmost evil. It is possible to infer 
almost anything from discontinuous observation. The simplest 
eases illustrate this. Only recently a friend, an ardent micro- 
scopist, announced to me his discovery of a perfect demonstration 
of “ heterogenesis.” We had some days before made an acci- 
dental gathering of the finest specimens of Volvox globator which 
I had ever seen. These were placed in a small clean trough, 
with clear water. With 100 diameters nothing of moment was 
visible but the volvoxes. The trough containing them was put 
* u Further Researches into the Life-History of the Monads.” Dallinger 
and Drysdale. *M. M. J.’ vol. xiii. p. 189. 
