172 GENERAL HISTORY OF THE IXPUSORIA. 



above assumed, runs from right to left. Each of the halves cut off by the 

 division then exj)ands somewhat in the direction from left to right ; a new 

 constriction soon presents itself in the direction from above downwards; 

 when this is complete, the originally globular primordial cell is divided into 

 foui' quarters (XIX. 40). 



'' This process of constriction and cutting oif is repeated once more, each 

 secondary cell becoming divided by a new septum into two equal halves 

 (XIX. 41-56). 



" This process of division, by which each primordial cell produces in the 

 first generation two, in the second foui', and in the third eight secondary cells, 

 is completed in the course of the night, so that early in the morning, in the 

 long summer days even by 3 o'clock, we perceive each of the eight primordial 

 cells divided into eight in the manner described (XIX. 41, 42). The gene- 

 rations produced in each case by this triple subdivision vary in the duration 

 of their lives and in their capacity of development ; the first two rapidly 

 divide again, and therefore are, according to Xiigeli's expression, mere 

 ' transitional generations ; ' the third alone arrive at complete development 

 and persist a long time as such ; these form the 'permanent generation,^ 



*' The process of division does not always take place simultaneously in all 

 the eight primordial cells of Steplianosjyhcera ; we not unfrequently find inside 

 the same envelope- cell some primordial cells still wholly unaltered, Avhile 

 others are already preparing to divide into two, a third perhaps abeady into 

 foui% and a fourth has abeady resolved itself into its eight secondary cells. 

 Very often most of the primordial cells are found already completely sepa- 

 rated into eight, while one or other of them is still whoUy unaltered. 



'*' When the act of division has gone on favoui-ably up to the point to which 

 we have followed it above, some houi's elapse before the young families of cells 

 escape completely from the envelope. The process which precedes their birth 

 consists principally in the more complete isolation, in a centiifugal direction 

 around their common centre, of the secondary cells produced by each pri- 

 mordial cell. Since the parting off" of the secondary ceUs advances gradually 

 from the periphery towards the centre, they are ah-eady completely indivi- 

 dualized and separated by intercellular spaces at the periphery, while aU eight 

 remain still connected in the centre into a common colourless mucous mass 

 filled with protoplasm-granules (XIX. 42). But the flow of the contents fi'om 

 the centre to the borders, which continues up to this time, at length causes 

 the constriction of the central mass of protoplasm also into eight parts ; the 

 eight secondary cells then appear of a deep yellowish green externally, passing 

 internally into colourless green towards finely granular beaks which are all 

 connected in the centre, but become gradually attenuated, torn away, and 

 retracted. Then the young primordial cells become rounded into short 

 eyhnders and stand in a circle, mthout organic connexion, but placed closely 

 beside one another : seen from above (in the polar view), under the micro- 

 scope, they resemble a wheel mth eight notches ; from the side, examined in 

 the equatorial view, we see four or eight short cylinders lying side by side, — 

 so that the whole is not unhke a small Sceneclesmus ohtusus (XIX. 57—58). 



" The primordial cell undergoing division behaves as a ivhole towards 

 external things, until the parting ofi" into eight is quite completed ; that is to 

 say, its two cilia move uninterruptedly, and consequently the entii'e Ste- 

 phanosj>ha^ra-g\obo still rolls through the water according to the known laws, 

 even when most of its primordial cells have abeady become more or less com- 

 pletely divided into four or eight secondary cells. Only shortly before the 

 completion of the division do the cilia of the parent- cell lose their motion and 

 disappear, it may be by being retracted or by being thrown off"; but the 



