260 



Prof. H. C. Bastian on Heterogenetic 



[Mar. 21, 



I have also myself, quite recently, watched with the greatest interest all 

 the stages of such a process, terminating in the evolution of fine speci- 

 mens of Paramecium, and am most pleased to be able to bear my testimony 

 to the general accuracy of M. Pouchet's description. Up to this period I 

 had never seen a single Paramecium or other specimen of the larger ciliated 

 Infusoria in any of my hay-infusions, these having all been prepared either 

 with warm or with hot water. But about ten days previously, on re- 

 reading M. Pouchet's description of the mode of evolution of these 

 organisms, it struck me that I had failed to see these phenomena, owing 

 to my never having made any infusions with cold water. I therefore at 

 once prepared such a maceration, and two or three days afterwards wrote 

 to M. Pouchet on the subject. In the reply which he was kind enough to 

 address to me, he said: — " Jamais, jamais vous ne renconterez un seul 



infusoire cilie dans une experience faite a Teau chaude II faut pour 



cela operer sur des macerations faites a froid ; alors vous obtiendrez facile- 

 ment le phenomene de developpement des ceufs spontanes des Paramecies, 

 dans les membranes proligeres qui se seront formees d'abord"*. 



On the evening of the day on which I received this letter, I again 

 examined the thick pellicle which had formed on the maceration of hay; 

 and, much to my delight, I found it studded with thousands of embryo 

 Paramecia, whilst others were free and active in the infusion. It was, 

 therefore, a most significant fact that they should have been met with on 

 the very first occasion that a cold maceration had been employedf ; whilst 

 not a single Paramecium had ever been seen before in any of the many hay- 

 infusions kept in the same placej, although several of them had even been 

 made with water whose temperature was not more than 125°- 1 30° F. — 

 and, therefore, not high enough to have killed any embryos which might 

 have chanced to preexist in the infusion previously to its filtration. 



The maceration was at the time covered by a thick pellicle, which had 

 become brown on its upper surface. Its under layers, however, were still 

 soft and pulpy. When a small portion of it was transferred to a micro- 

 scope-slip, and gently compressed by the covering-glass so as to flatten it 

 out into a thinner layer, the granular membrane was observed to be pretty 



* M. Pouchet has been in the habit of using one part by weight of ordinary dry hay 

 to about forty parts of water, and then allowing the maceration to stand for two or three 

 hours before filtering off the clear liquid. 



t Owing to the coldness of the weather (the daily temperature of the room being 

 scarcely above 60° F.), they did not make their appearance in the pellicle till more than 

 fourteen days, although with a daily temperature of 75° F. they are said by M. Pouchet 

 to begin to make their appearance on the third or fourth day. I had examined the 

 pellicle of my maceration from time to time during the first week, but did not look at 

 it subsequently for several days — not, in fact, until the day on which I received M. 

 Pouchet's letter. During the first week the pellicle had become very thick and pulpy, 

 but, the weather being rather colder at this time, it was principally giving birth to various 

 kinds of Fungus-germs. 



\ Beneath a bell-jar in my study. 



