440 M. Balbiani on the Generative Organs 



I had also been led, in a great number of cases, to regard what 

 nearly all authors had considered to be a spontaneous division 

 in a longitudinal direction, as a sexual union of two individuals. 

 Very often, in fact, I have been able to ascertain that this state 

 coincided with certain remarkable changes which took place in 

 the internal organs of these animals. 



I. The corpuscle which, in the Infusoria, has been described 

 under the name of nucleolus, and which I have shown to be the 

 male genital gland, has hitherto only been indicated in a few 

 rare species. In connexion with this, I have examined a great 

 number of individuals belonging to numerous and varied forms, 

 and I have convinced myself that, far from constituting an ex- 

 ception, the presence of one or even several nucleoles was a nearly 

 constant fact in the different types of this class ; but frequently 

 the simple or multiple nucleole which they contain is so inti- 

 mately confounded with the substance of the nucleus, that it only 

 becomes apparent when it is separated therefrom accidentally by 

 the action of reagents, or spontaneously at certain determinate 

 periods in the life of these creatures, principally at the time of 

 their sexual propagation. I have counted fourteen species in 

 which this organ was very evident to me, and in which I have 

 also been able to follow its evolution, to a greater or less extent, 

 at the breeding season, at the same time that I was an eye- 

 witness of the other actions which concur in assuring the repro- 

 duction of these animalcules by fecundated germs. 



As regards the number and situation of the testicular organ 

 of the Infusoria, I have met with the following varieties. It is 

 simple, rounded, and lodged in more or less deep depressions of 

 the nucleus in Paramecium Aurelia and P. caudatum, and also 

 in a third species nearly allied to P. Bursaria, but smaller and 

 destitute of green granules. The genus Bursaria (B. leucas, flava, 

 and vernalis) also presents a simple nucleole situated in the vici- 

 nity of the nucleus. The same thing occurs in Chilodon cucul- 

 lulus. But with regard to the latter, I must remark that I do 

 not regard as the analogue of the nucleole of the preceding spe- 

 cies the corpuscle to which M. von Siebold has given this name, 

 and which is placed in the interior of the granular mass of the 

 nucleus, in the centre of a broad transparent zone. The true 

 nucleole or testicle of Chilodon appears in the form of a small, 

 rounded, brilliant grain, provided with a proper membrane, and 

 situated quite to one side and towards the middle of the nucleus. 

 It is very easily perceived in large specimens by employing the 

 action of reagents. As regards the nucleus and its internal 

 parts, I make no difficulty in regarding them as representing all 

 the elements of an ovum, of which the nucleole of the celebrated 

 German naturalist would be nothing but the germinal spot. The 



