80 CRITIQUES AND ADDRESSES. [iv. 



the yeast as to make it muddy, though the largest are 

 not more than one two-thousandth of an inch in diameter, 

 and the smallest may measure less than one seven- 

 thousandth of an' inch, are living organisms. They 

 multiply with great rapidity, by giving otf minute buds, 

 which soon attain the size of their parent, and then either 

 become detached or remain united, forming the compound 

 globules of which Leeuwenhoek speaks, though the con- 

 stancy of their arrangement in sixes existed only in the 

 worthy Dutchman's imagination. 



It was very soon made out that these yeast organisms, 

 to which Turpin gave the name of Torula cerevisicv, were 

 more nearly allied to the lower Fungi than to anything 

 else. Indeed Turpiu, and subsequently Berkeley and 

 Hoffmann, believed that they had traced the development 

 of the Torula into the well-known and very common mould 

 the Penicillium glaucum. Other observers have not 

 succeeded in verifying these statements ; and my own 

 observations lead me to believe, that while the connection 

 between Torula and the moulds is a very close one, it 

 is of a different nature from that which has been supposed. 

 I have never been able to trace the development of Torula 

 into a true mould ; but it is quite easy to prove that 

 species of true mould, such as Penicillium, when sown 

 in an appropriate nidus, such as a solution of tartrate of 

 ammonia and yeast-ash, in water, with or without sugar, 

 give rise to Tor idee, similar in all respects to T. cerevisice, 

 except that they are, on the average, smaller. Moreover, 

 Bail has observed the development of a Torula larger 

 than T. cerevisice, from a Mucor, a mould allied to 

 Penicillium. 



It follows, therefore, that the Torulce, or organisms of 

 yeast, are veritable plants ; and conclusive experiments 

 have proved that the power which causes the rearrange- 

 ment of the molecules of the sugar is intimately connected 



