Male Sexual Organs ? of the Infusoria, 47 



these two vesicles towards all parts of the body ; they enlarged 

 themselves by degrees when the vesicles contracted, and then 

 contracted and disappeared when the vesicles dilated. Every 

 one of these canals presented a swelling or bulging out at its 

 base, near to the vesicles. These two organs resembled two 

 small transparent Aphiures, which had been enclosed in the bodies 

 of the Paramecia ; they were all alike in all the specimens. — 

 (See Pi. I. fig. 6, c.) 



At a still later period M. Ehrenberg employed another 

 mode of observation, which was still easier than that which we 

 have just described. He placed on an object-glass a drop of 

 water which contained a great number of these infusores, 

 and then removed as much of the liquid as he could ; so that 

 the little beings crowded in the midst of fluid could no longer 

 swim freely. Placed in this situation all these infusores be- 

 came larger in consequence of the softness of their bodies, and 

 exhibited in the clearest way possible the contractions and di- 

 latations of their two great organs. He has observed these con- 

 tractile organs, in every respect alike, in twenty-four species 

 which he enumerates, belonging to genera of three different far 

 milies ; but with these details we shall not trouble our readers. 



At the same time we remark, that these organs, both as it re- 

 gards their number, or the situation of the central part of the 

 apparatus, present essential differences in the twenty-four spe- 

 cies in which they were found. Thus in six of them, and we 

 shall only name the Paramecium aurelia, there are found to be 

 two central parts of this system, one of which is in the middle 

 of the anterior part of the body, and the other in the posterior 

 part. All these infusores, too, with one exception, are known to 

 divide transversely and spontaneously into two portions, and in 

 these cases each part preserves one of the central points of this 

 apparatus ; and this twofold organization appears to have a re- 

 lation to the division which has previously been mentioned. 

 Sometimes also, the professor has observed that at certain epochs, 

 there were four of these central points in many of these infu- 

 sores; whilst at other times, there were only two in indivi- 

 duals of the same species. When there were four, there were 

 always two in each half of the body ; and all the infusores which 

 resent this number are capable of dividing themselves trans- 



