1877.] 



On the Development of Organisms. 



503 



In counting the drops on the plate, judgment is required in distinguish- 

 ing drops that have split off the rays from those that have split off later 

 from the arms. Often the arrangement on the plate is so confused that 

 no estimate can be made ; at other times great regularity of the arrange- 

 ment gives a probability almost amounting to certainty to the estimate. 



The number of arms, as in fig. 8, Set 1, was estimated by judging of 

 the angle between alternate arms. The estimate was sometimes con- 

 firmed by drops splitting off the arms and being left on the plate, as in 

 the case of the rays. Thus I am pretty certain that, with a height of 

 fall of 270 millims., the number of arms was often 18. 



I may mention that I have obtained " patterns " on thinly smoked 

 glass, made by drops of oil and mercury falling in an approximate 

 vacuum of a pressure of 20 millims. of mercury. The marks thus ob- 

 tained differ from those made in air, the central spot of lampblack being 

 smaller in the case of air. Tor low heights of fall the difference is not 

 perceptible, but it becomes very marked as the height is increased from 

 100 to 500 millims. 



With a liquid which wets the surface on which it falls (as, for in- 

 stance, milk on glass) I find that the earliest stages are very similar to 

 the first two of Set 1 ; but no well-marked main rays are seen, as in fig. 3. 

 The annular ridge of fig. 4 is seen to overflow the slightly protruding 

 rays, and form a figure like number 7, with slight undulations which do 

 not afterwards increase into arms. 



It is, I think, worthy of remark that in the case of mercury on 

 smoked glass, where the adhesion is least, the main ridges appear early 

 before the drop is much spread out. On a clean glass, where the adhe- 

 sion is greater, the main ridges first appear rather later, and are some- 

 what less strongly marked ; while with milk on a clean glass, to which it 

 adheres strongly, no ridges are seen at all. 



IV. '^Preliminary Note on the Development of Organisms in 

 Organic Infusions." By John Tyndall, F.R.S. Received 

 January 18^ 1877. 



I beg leave to submit to the Eoyal Society a brief preliminary note of 

 the results obtained in the further prosecution of my researches " On the 

 Optical Deportment of the Atmosphere, with reference to Putrefaction 

 and Infection." 



The very remarkable experiments of Dr. Eoberts, of Manchester, which 

 have been confirmed by Professor Cohn, of Breslau, have been both verified 

 and contradicted by my recent researches. In some cases alkalized hay- 

 infusions have been completely sterilized by boiling for five minutes, in 

 other cases they have withstood the boiling temperature for a far longer 

 period. 



