228 PROGRESS OF MICROSCOPICAL SCIENCE. 



ill the Society's ' Transactions' in 1871, respecting which Professor Wil- 

 liamson showed that it possessed a vascular axis exhibiting a triquetrous 

 transverse section, the author gave his reasons for believing that the 

 strobilus was the fruit of Aster -ophyllites. In a letter addressed to Dr. 

 Sharpey on Nov. 16, 1871, and published in No. 131 of that Society's 

 ' Proceedings,' Professor Williamson gave a brief description of a stem 

 having a similar triangular vascular axis, with lenticularly thickened 

 nodes, and which he again referred to the same verticellate-leaved 

 genus. In a second letter to Dr. Sharpey, dated May 3, 1872, the 

 author confirmed the above conclusions by stating that he had "got an 

 additional number of exquisite examples showing not only the nodes 

 but verticels of the linear leaves so characteristic of the plant. These 

 specimens place the correctness of my previous inference beyond all 

 possibility of doubt, and finally settle the point that asterophyllites is 

 not the branch and foliage of a calamite, but an altogether distinct 

 type of vegetation having an organization peculiarly its own." The 

 author said that he had obtained the plant in almost every stage of its 

 growth, from the youngest twig to the more matured stem, and that the 

 genus would be the subject of his next, or fifth, of the series of memoirs 

 now in course of publication by the Poyal Society. 



Experiments on the question of Biogenesis. — Dr. William Eoberts 

 exhibited, at one of the meetings of the Manchester Philosophical 

 Society (February 4th), some preparations and experiments bearing on 

 the question of biogenesis. He stated that in the last two and a half 

 years he had performed over 300 experiments. His results supported 

 the conclusion that the fungi, monads, and bacteria which make their 

 appearance in boiled organic mixtures, are not due to spontaneous 

 evolution, but arise exclusively under the influence of pre-existing 

 germs or ferments introduced from without. His method of experi- 

 menting consisted chiefly in exposing organic solutions and mixtures 

 to a boiling heat in glass flasks whose necks had been previously 

 tightly plugged with cotton wool. Two modifications of the experi- 

 ment were adopted. 



I. In the first modification a 4-ounce flask was employed, and the 

 heat applied directly by means of a gas flame. 



II. In the second modification— after the introduction of the mate- 

 rials to be operated on — the elongated neck of the flask was sealed 

 hermetically by the blowpipe above the plug of cotton wool ; the 

 flask was then weighted with a collar of lead and immersed in a large 

 can of water ; the can was then put on the fire and the water boiled 

 for 20 or 30 minutes. During the process of boiling, the flask was 

 maintained in an upright or semi-upright position, in order to prevent 

 any wetting of the cotton-wool plug by the contents of the flask. 

 When the can was cold the flask was removed, and its neck filed off 

 above the cotton wool, so as to permit free ingress and egress of air. 



Flasks thus prepared were maintained at a warmth varying from 

 50° to 90° Fahr. for long periods — many weeks and months — some in 

 the dark and some exposed to the light with the following results : — 



I. Simple filtered infusions of animal or vegetable tissues — a very 

 considerable variety were tried — boiled over the flame for five or ten 



