322 PKOCEEDINGS OF SOCIETIES. 



faint outline ; in the " black " form they were still elliptic, but 

 relatively to their width much, and absolutely somewhat, shorter, 

 and showed a dark, it might be said thick, outline. The latter, or 

 "black " form, was more prone to show tbe cells arranged in such a 

 position in twos or fours, as was indicative of recent self- division. 

 Four could sometimes be seen in a plane, their inner surfaces of 

 contact of a thinner appearance, flat and sub-rectangular within 

 at the central common point of union. Both, under a high (i") 

 power, showed a hyaline, not deep, rather sharply marked, "halo" 

 surrounding the cells, the former {M. prodigiosus) more noticeably. 

 The latter showed a " molecular " motion much more vividly than 

 the former ; it need not be said that no other motion was evinced. 

 In both forms the colouring substance showed imbedded therein 

 a more dense, as if granular, body, posed in the former more 

 towards one end of the cell, and very minute ; in the latter more 

 nearly central, by comparison considerably larger. To call this 

 granular body in either a " nucleus " would, of course, be far too 

 great a begging of the question. Mr. Archer had called the inner 

 substance " colouring substance," for, as previously mentioned, 

 it gave to the eye a very iVos/oc-like hue. The colour of the mass 

 seems thus to be due mainly, if not altogether, to the tenacious 

 medium binding the cells into a common stratum, and it is, to a 

 great extent, borrowed by any mycelioid filaments should they be 

 present. This colour in the aggregate Prof. Cohn regards as 

 being of " specific " value, or, to say the least, of " race " value ; 

 that is, as indicating forms or types, which, by a continuous 

 heredity, run on and on, each, as it were, in its own groove. 

 Prof. Cohn supposes that the fitful and rather isolated manner in 

 which these productions seem to occur is explained by their 

 " germs " being carried from one suitable 7iidus to another by the 

 atmosphere. Here, however, were two forms quite distinguish- 

 able by the eye, either in the mass or under the microscope, oc- 

 curring one on each of two pieces of the same potato ; one of 

 these forms Mr. Archer had " sown," the other " came there," 

 and both were under the same bell-glass. The original (boiled) 

 potato was in no way " diseased " (he knew from practical ex- 

 perience, indeed, it was excellent, having eaten the rest of it some 

 days before at dinner ; he would rather not venture on th'e 

 remainder now !). Probabilities, he thought, were much in favour 

 of Prof Cohn's views, but Mr. Archer gave this little history 

 quantum valeat. 



