332 GENERAL HISTORY OF THE INFUSORIA. 



in fact, I have been able to ascertain that this state coincided with cer- 

 tain remarkable changes which took place in the internal organs of these 

 animals." 



The following is the general summary of the results M. Balbiani has 

 arrived at : — " 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 numer- 

 ous and varied forms, and I have convinced myself that, far from constituting 

 an exception, the presence of one or even several nucleoles was a nearly con- 

 stant fact in the different types of this class ; but frequently the simple or 

 multiple nucleole which they contain is so intimately 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 conciu" in assuiing 

 the reproduction of these animalcules by fecundated germs. 



" As regards the number and situation of the testicular organ of the Infu- 

 soria, 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 sj^ecies, nearly alhed 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 vicinity of the 

 nucleus. The same thing occurs in Chilodon Cucullulus. But with regard to the 

 latter, I must remark that I do not regard as the analogue of the nucleole of the 

 preceding species 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 disappearance of the clear zone and 

 of its central corpuscle in the animals which have just copulated, especially 

 appears to me to militate in favour of this view. 



" II. I have met with a multiple testicle in many species belonging to the 

 groups of the Oxt/trichince and of the Euplotes or PJoesconice, including the 

 highest types of this class. In the genus Oxytricha the two nuclei, which 

 are elongated in the direction of the greater axis of the body, are each accom- 

 panied by a small, rounded, testicular body, very distinct from the correspond- 

 ing nucleus. There are also two, placed one to the right and the other to 

 the left of the long nucleus, which is curved into the form of a horse-shoe, 

 in Euplotes Charon and E. viridis. In the genera Stylonychia (S. Mytilus, 

 pustulata, and lanceolata) and Urostyla {U. grandis) the nucleoles, to the 

 number of four or five, are distributed in two groups in the vicinity of the 

 nuclei, of which the anterior is accompanied by two, and the posterior also 

 by two or sometimes three, of these little organs. They are remarkable from 

 their distinctly-rounded outhne, their great refractive power, and their 

 homogeneous structure. In Spirostoynmn amhiguum, each of the grains of 



