MR. RAY LANKESTER'S letter in last week's NATURE affords fresh evidence of his lack of acquaintance with the several stages through which the â spontaneous generationâ controversy has passed, or he would not now cite as a â most important resultâ only made known by recent experimentation, a fact which has been well known and repeatedly verified since the time of Spallanzani. I allude to the influence of the prolongation of the period of exposure to heat in retarding or altogether arresting the putrefactive tendencies of organic solutions. I have not thought it needful on previous occasions to point out the various misconceptions and the apparent ignorance of facts shown by Mr. Lankester in his querulous communications to your columns on the subject of â Spontaneous Generation.â There are one or two points, however, to which I will now venture to solicit his attention, and that of your readers generally.