M. RaspaiPs experiments on the granules of Pollen. 99 



Sth^ The inclination of the object-plate, — It is almost impos- 

 sible to obtain a geometrical horizontality with respect to the 

 object-plate of a microscope, and the nearer we approach to 

 this point of perfection, the more the movements of the cor- 

 puscles suspended in the liquid are illusory. The liquid ap- 

 pears to direct itself towards the point opposite to>the side 

 the most inclined, on account of the inversion of the image ; but 

 we often then observe two motions in opposite directions, and 

 lying above each other. If an islet is encountered in the way 

 of the corpuscles, they are then seen to turn the obstacle by 

 an act of prudence which can only proceed from a sort of fluid 

 atmosphere, with which all solid bodies are enveloped in water. 

 The illusion of a spontaneous motion becomes greater still, 

 when the islet or promontory is near the limits of the field of 

 the microscope. 



But, however illusory we may suppose these various mo- 

 tions, it is easy to distinguish them from the motions which 

 are directed or determined by the will ; it is enough for this 

 purpose to observe even superficially the motions of the mo- 

 nads or other infusory animalcules. I should not have been 

 obliged to enter into these details, if the opinion which I op- 

 pose had not been revived with a publicity so solemn, that I 

 felt it incumbent on me to repeat all my experiments, and to 

 vary them in every way, as if I had doubted the accuracy 

 of my former ones. 



II. For this purpose I made use of the pollen of the Malva- 

 ceae, not only because it has the greatest proportions, but 

 also becau&s it has been used to establish an opinion contrary 

 to mine. Nothing new took place, and if I enter here into some 

 details, it is less to publish discoveries than to make up for 

 my former silence, and to pursue the question relative to spon- 

 taneous motion even to its last entrenchments. 



1^^. The grains in issuing from the pollen aflPect different 

 forms and diameters. 



2d. It sometimes happens that two agglutinate together in 

 order to form a third, whose diameter then equals that of the 

 two first. 



Zd. If several grains join together, they often form a line 

 more or less crooked or sinuous, which, giving way, appears to 

 bend, especially when it is met by two opposite currents. 



