M. Balbiani on Sexual Reproduction in the Infusoria. 437 



gins it presents notches, whieh, penetrating more and more deeply 

 into its mass_, isolate one or more fragments, in which a sufficient 

 magnifying power enables us to see a certain number of small 

 transparent spheres with an obscure central point. In other 

 cases the nucleus, whilst still almost entire, presents this aspect, 

 and then appears as if stuffed with these little rounded bodies, 

 the analogy of which to ovules cannot be doubted in the least. 

 The evolution of the nucleus and nucleolus being identical and 

 progressing at the same rate in the two coupled individuals, it 

 follows, if from this moment we regard the former as an ovary, 

 and the second as a testicle or seminal capsule, not only that each 

 of them possesses the attributes of both sexes, but that they fecun- 

 date each other, and serve at the same time as male and female. 

 As regards this fecundation itself, everything seems to prove that 

 it takes place by means of an exchange made by the two coupled 

 individuals of one or more of their seminal capsules, which pass, 

 through the apertures of the mouths closely applied against 

 each other, from the body of one Paramecium into that of the 

 other j for, very often, although we may not be able to perceive 

 this passage itself, we may at least detect the moment when one 

 of the capsules already engaged in one of the mouths, is on the 

 point of clearing this aperture. Does the exchange which causes 

 fecundation take place with all the capsules in a single copula- 

 tion, or in so many successive copulations with different indi- 

 viduals ? This is a question the solution of which is not easy, 

 and which, to keep within the field of our observations, we shall 

 not attempt to solve at present. 



However this may be, each capsule, after its transmission, 

 still continues to increase in size in the body of the individual 

 which has received it, for we have never found any which had 

 attained the limit of their development in individuals which were 

 still coupled. They then frequently attain a volume greater than 

 that of the nucleus itself, but there is never more than one that 

 arrives at maturity at the same time. When, having arrived at 

 this state, it is examined after being pressed out of the body of 

 the animalcule, to free it from the granulations which mask it 

 more or less while there, it appears under the form of a large 

 ovoid body, the surface of which presents a multitude of parallel 

 striae directed longitudinally, and due to the arrangement in 

 series of the corpuscles contained in the interior. Compres- 

 sion carried so far as to cause its rupture, show^s it distinctly to 

 be formed by a membrane of extreme tenuity, and contents, en- 

 closing an innumerable quantity of small fusiform corpuscles, of 

 which the extremities are completely lost to sight in consequence 

 of their extreme fineness. As soon as they are free, these little 

 bodies show themselves to be animated by a vacillatory and 



