REPRODUCTION IN THE INFUSORIA. 287 



pieces as tliere are eggs destined for maturity. Hence, to 

 estimate aright the correlation which has just been indicated, 

 it is only at the reproductive period that one can properly 

 examine the number of elements to which each primitive 

 sexual organ has given birth /^ 



In Stylonychia mytilus, an Infusorium which, at the repro- 

 ductive period, possesses several male elements already formed, 

 the further development of their contents is as follows : — 

 First, each undergoes " a sort of distension during which its 

 membranous envelope separates a little from the contents 

 to which it was before closely applied. At the same time 

 these contents, which were at first remarkable for their 

 homogeneous consistence, and refractive aspect, become 

 paler, more transparent, and better enable one to recognise 

 the fine molecular granules of which they are made up. Each 

 spermatic globule is then transformed into a minute round 

 vesicle, enclosing within it a free granular mass or " nucleus.'" 

 Out of this granular mass the evolution of spermatozoa takes 

 place. One may note, in fact, at a somewhat later period, 

 that the vesicle has increased in size, and the nucleus assumed 

 a slightly flattened, hemispheric or discoidal, form. At the 

 same time it has drawn nearer to one point of the limiting 

 membrane. On that side Avhich looks to the interior of the 

 vesicle, this nucleus gives origin to a conical bundle of ex- 

 ceedingly delicate filaments agglutinated together, especially 

 towards the apex of the cone, which presents a brilliant homo- 

 geneous aspect, which is heightened by treatment with acetic 

 acid. This apex at length nearly touches the wall of the 

 vesicle, at a point opposite to that near which is situated the 

 gi'anular mass from which the spermatozoa have been evolved. 

 Those filaments which occupy the peripheric portion of the 

 bundle soon become detached from the common mass and 

 arrange themselves around the granular nucleus. The fila- 

 ments at its centre, hasten, in like manner, to separate one 

 from the other, and assume the same arrangement as their 

 predecessors. When at this period of its development the sper- 

 matic cell is placed with its granular mass uppermost, the 

 latter appears to occupy the centre of the cell, and from its 

 margin may be seen radiating a circlet of slightly curved 

 filaments, extending as far as the cell- wall. By degrees 

 the cell acquires an elongated oval form, the granules of the 

 nucleus become more and more rare, and the spermatic 

 filaments, abandoning their radiate disposition, arrange 

 themselves in two bundles with their bases opposed, and their 

 free extremities directed towards the two poles of the cell. 



