OF THE PROTOZOA. CILIATA. 333 



the long moiiiliform 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, Kondylostommn, Traclielius moniliger, &c. 



'' III. The evolution of the male genital apparatus of the Infusoria, as just 

 characterized, in the other species of the genus Paramecium does not differ 

 from that presented to us by P. Bursaria. In the Oxytricliina each of these 

 organs remains entii'e, becomes enlarged, and exhibits in its interior, applied 

 against its wall, a thick granular body, furnished with a tubular appendage, 

 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 aU directions in the interior of the capsule. Subsequently 

 the granular body and its duct disappear, and the filaments," becoming free, 

 coUect into a bundle, which fills the whole of the formative sac. Although 

 I have never seen them execute any movements, I do not hesitate in consi- 

 dering them as the spermatic filaments of these animals. 



" IV. It is with equal certainty that we may call the nucleus the female 

 genital organ of the Infusoria, in opposition to the perfectly hypothetical 

 assertion of Ehrenberg, who regards it as the testicle. Its evolution likewise 

 only commences at the time of reproduction, and often during the sexual 

 union itself. In P. Aurelia and P. caudatum, towards the end of the copulation, 

 its surface is traversed in aU directions by numerous ftuTows, which, penetrat- 

 ing deeper and deeper into its mass, finally divide it into a great number of 

 unequal and irregularly-rounded fragments, having a clear centre more or 

 less surroimded by granules. I should compare these with the first rudi- 

 ment of a vitellus, and the transparent central portion to a more or 

 less developed germinal vesicle. The fragments thus formed are soon dis- 

 persed in the siuTounding parenchyma. Here a very small number of them, 

 almost always foiu-, never more and very rarely less, complete their evolution, 

 and soon acquii-e the appearance of complete and well- developed ova. In 

 this state they present themselves in the form of small brilliant bodies, per- 

 fectly equal in volume, slightly oval, and of a bluish-grey appearance. We 

 may very clearly distinguish in them a finely- granular vitellus, surroimded 

 by its proper membrane, which separates from it more or less after a few 

 moments' exposure to water. The germinal vesicle and spot are also visible 

 with a distinctness truly surprising, considering that we have to do here with 

 the smallest of living organisms. I have met with these ova still enclosed in 

 the body of the animal on the seventh day after the copulation : they no 

 longer exhibited either germinal vesicle or spot ; and their volume had slightly 

 increased. In the allied species, P. Bursaria, the reniform nucleus becomes 

 unrolled before breaking up, and in this state resembles the ribbon-shaped 

 nucleus of the Vorticellce. About twenty or twenty-five of the fragments 

 produced from it continue their development and become so many perfect 

 ova. In the nucleus of Chilodon Cucullidus, also, we observe, after the copu- 

 lation, the disappearance of the transparent zone with its central obscure 

 spot. In the genera Stylonychia and Urostyla the ova are four in number. 



