Ward, — Recent Researches on the Parasitism of Fungi \ 7 
antisepsis, the theory of toxins and vaccination, and other outcomes of 
these fundamental researches of Cohn and De Bary — to which should be 
added those of Lister and Pasteur— must always occupy ; and we shall see 
that these are by no means the only directions in which exact botanical 
researches have effected far-reaching results on the well-being of mankind. 
It is more germane to my immediate subject to refer to another great 
question which the work of Cohn, De Bary, and Pasteur, brought to a series 
of tests which finally rid the world of a bugbear. 
The idea of spontaneous generation, although it had lost prop after 
prop, as the conditions of development of the more minute organisms were 
carefully and conscientiously examined, had for some time apparently 
secured a stronghold among the Bacteria, from which it seemed impossible 
to dislodge it. 
Cohn’s work ( 49 ) on the Hay Bacillus, in 1876, during the course of 
which he observed the formation of the endospores, brought forward very 
clearly the fact of the resistance of spores to extremes of temperature, and 
his experiments, together with those of Pasteur on the organisms of the 
atmosphere ( 125 ), 1862, and those of Tyndal ( 186 ), 1876, on discontinuous 
sterilization, laid the spectre of abiogenesis, which had repeatedly arisen at 
intervals since the time of Van Helmont ( 81 ), 1745, and Needham ( 119 ), 
and had recently been revived to great activity by Bastian ( 25 ) ; and we 
should observe that Cohn did not merely devise experiments which showed 
that a something or other got into a putrescible liquid and fermented 
it or not according to circumstances, but he showed what that something 
was — the spore of the Bacillus — and followed its development to complete 
proof of the relation it bore to the phenomenon. 
Yet another question of general importance arose in connexion with 
Bacteria. Several observers had laid stress on the fact that forms of 
definite shape, to which generic and specific names had been given by Cohn 
and others, altered their sizes and shapes during development, and assumed 
morphological characters which had been used to define other genera and 
species. Billroth ( 29 ), 1874, Nageli ( 1 16 ), 1 887, and Zopf ( 208 ), 1 882, carried 
their views so far as to deny, more or less categorically, any constancy of 
form whatever among these organisms, or even to assert that all the forms 
were derived from one or a few only. It seems strange to us at this 
distance of time that so much research should have been necessary to prove 
that the so-called pleomorphism of the Bacteria was merely due to the 
species in question having been described and named by different observers 
who saw them in different stages of development. Exactly similar con- 
ditions of affairs would arise if an Oak seedling was named by a man who 
knew not the tree, and the latter by another who did not know it was 
developed from the former. 
