and Reproduction of the Infusoria. 441 



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 be- 

 longing to the groups of the Oxy trichina and of the Euplotes or 

 Plcesconia, 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 accompanied 

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

 responding 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 viridis. In the 

 genera Stylonychia (S. Mytilus, pustulata t 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 outline, their great 

 refractive power, and their homogeneous structure. In Spirosto- 

 mum ambiguum, each of the grains of the long moniliform cord 

 which here replaces the oval nucleus of the other species, gives 

 lodgment, in a deep depression of its surface, to a small rounded 

 corpuscle, which corresponds with the nucleole of the preceding 

 species ; this brings the number of testicles in this animal to 

 forty-five or fifty. I have only been able to perceive them in 

 individuals which have been copulating for a certain time, and 

 by employing dilute acetic acid. It is very probable that an 

 analogous arrangement will be found in the other types in which 

 the nucleus is formed of grains placed in a single row, like a 

 necklace, such as Stentor, Kondylostomum, Trachelius moni- 

 liger, &c. 



III. The evolution of the male genital apparatus of the Infu- 

 soria, as just characterized, in the other species of the genus 

 Paramecium does not differ from that presented to us by P. Bur- 

 saria. In the Oxytrichince each of these organs remains entire, 

 becomes enlarged, and exhibits in its interior, applied against 

 its wall, a thick granular body, furnished with a tubular append- 

 age, which projects into the cavity of the capsule, and appears 

 to be open at its free extremity. This tube, which seems to be 

 an excretory duct, often appeared to be filled with capillary 

 filaments of extreme fineness, arranged parallel to the axis of the 

 duct in question, in which they were fixed by a portion of their 

 length, whilst the remainder, escaping by the orifice of the tube, 

 radiated in all directions in the interior of the capsule. Sub- 

 sequently the granular body and its duct disappear, and the 

 filaments, becoming free, collect into a bundle, which fills the 



