REPRODUCTION IN THE INFUSORIA. 179 



from the body of the Infusorium, and allowed to remain in 

 contact with the surrounding fluid. 



The granular substance, which so completely occupies the 

 interior of the ovary, is itself nearly ti'ansparent, and of a 

 yellowish-grey tint when seen by direct light, but appears, 

 at times, sufticiently refractive. Its colour is heightened by 

 the addition of acetic acid. From this stroma the future 

 eggs are developed. " Often we may perceive within it clear 

 rounded spaces, more or less concealed beneath the granules 

 which cover them. These transparent particles can evidently 

 be nothing else than germinal vesicles, scattered throughout 

 the midst of a common yolk-mass. At other times each of 

 these vesicles appears to be surrounded by a special granular 

 zone, which indicates the first separation of the young ova 

 from one another. This appearance almost always coincides 

 with an increased scarcity of the granular particles in the 

 common mass between the ova, and the existence of a narrow 

 transparent border around each of these first rudiments of 

 the egg. Very dilute acetic acid, and an aqueous solution 

 slightly tinted with carmine dissolved in ammonia, are the 

 two best reagents wherewith to study these diverse aspects 

 of the ovary. The granular and transparent portions of the 

 latter organ, by attracting with different degrees of intensity 

 the colouring matter of the carmine solution, display in a 

 very clear and beautiful maimer their mutual relations. 

 But, without the aid of any preparation whatever, by simply 

 selecting the most favourable species for the observation of 

 such phenomena, the arrangement and the signification of 

 these particles become, so to speak, of their own accord, suf- 

 ficiently obvious. The nucleus of Chilodon cucullulus is par- 

 ticularly favorable for the demonstration of what \re seek 

 here to establish. In the midst of the granular substance 

 which fills the greater portion of this organ, may be seen a^ 

 large and beautiful, perfectly transparent vesicle, bearing at its 

 centre an opaque and rounded corpuscule. It is impossible not 

 to be at once struck by the complete resemblance to a cell which 

 the nucleus, viewed as a whole, presents. This comparison, 

 made for the first time by the illustrious leader of the unicel- 

 lular school, M. V. Siebold, led him to designate the central 

 corpuscle under the name of nucleolus.'^ Yet one may venture 



* " This intra-}inclear nucleolus must not be confounded with the bodies 

 which, in other Infusoria, bear Ihe same name, but are situate on the 

 exterior of the nucleus. Tliese last belong to the male sexual apparatus, 

 according to the view above laid down; while the first is, in truth, an 

 element of tiie cell wliich the egg represents. Chilodon itself possesses, in 

 addition, a nucleolus or testis, placed on the outside of the nucleus." 



VOL. II. NEW SER. N 



