174 HETEROGENETIO ORIGIN OF 



with the formalin solution. The bottle was subsequently left in a 

 cupboard for seventeen weeks, the temperature of which, for a 

 long time, remained about 70° F., though it afterwards fell to 50° F. 



When removed from the bottle at the expiration of this time the 

 potato was found to be quite firm and not at all shrunk. On 

 section it was seen to be discoloured to a pale earthy tint, with 

 mottlings here and there of a rather darker colour. The cut 

 surface was moist and had a distinctly acid reaction, and there was 

 not the least sign of softening or disintegration anywhere. Thin 

 sections having been made, they were shaken up in a small tube 

 with distilled water, so as to get rid of the starch-grains from many 

 of the cells, and the sections were subsequently allowed to soak 

 for two hours in some of Westphal's mastzellen stain, diluted 

 with two per cent, formalin. 



On microscopical examination of these sections, groups of 

 Bacteria were found in large numbers of the cells, though not in 

 those near the surface. The contents of one of these cells is 

 shown in Fig. 4, B ( X 500) ; some of the Bacteria were free and others 

 were in, or lying on, the primordial utricle ; but, as I have usually 

 found with microorganisms in such situations, they were not 

 appreciably stained. Some cells, which did not contain obvious 

 Bacteria, showed plenty of minute cocci-like bodies on the surface 

 of the primordial utricle, also not taking the stain, which probably 

 represent early stages of the Bacteria (Fig. 4, A, x 700). 



Another larger potato, about two inches in diameter, was treated 

 in exactly the same way as the last in September, 1901, and after 

 the bottle was finally closed, it was left on the surface of an 

 incubator at a temperature of about 80° F. for seven weeks. 



When examined the potato was not found to have shrunk, or to 

 be appreciably altered on the surface. On section, it was moist, of 

 acid reaction, and showed as before a pale earthy colour with 

 rather darker mottlings in places. 



Sections were made and treated in the manner previously 

 indicated, and, on examination, multitudes of Bacilli were seen here 

 and there in cells in all parts of the section except for about one- 

 fifth of an inch from the surface. In places, also, theie were fine 

 mycelial filaments containing spore-like bodies. Some of these 

 Bacilli took the stain fairly well as maybe seen in Fig. 5, A (x 500), 

 in which the two kinds of organisms are shown. In or on the 

 primordial utricle also there were multitudes of very delicate 

 interlacing filaments (? Bacilli), containing an abundance of spores 



