THE CELL 



PIG. 167. Development of Pandorina morum (after Pringsheim ; from Sachs, Fig. 411) : 

 .1 a swarming family ; If a similar family, divided into sixteen daughter-families; III a 

 sexual family, the individual cells of which are escaping the gelatinous investment; IV, 

 V conjugation of pairs of swarmers; VI a zygote, which has just been completed; FII 

 a fully grown zygote; Fill transformation of the contents of a zygote into a large swarm- 

 cell ; IX the same after being set free ; X a young family developed from the latter. 



swim about independently (Fig. 157 III, IV). These swarm- 

 cells, which are oval, and (with the exception of the anterior, 

 somewhat pointed, hyaline end) are green in colour, possess a red 

 pigment spot and two flagella ; they are somewhat unequal in 

 size. However, in this respect a marked sexual differentiation 

 is not apparent in Pandorina. For when swarm-cells from two 

 different colonies approach each other, it is seen amongst the 

 crowd that sometimes two small ones, sometimes two large ones, 

 a-nd sometimes one large and one small unite together (Fig. 157 



IF, n 



