11 



(Vaucheria), they may also have a red "eye spot" and vacu- 

 oles, which are sometimes pulsating, i.e. they appear and re- 

 appear at certain intervals. The swarmspores move about in 

 the water in irregular paths, and apparently quite voluntarily, 

 revolving round their longer axes ; but they come to the sur- 

 face of the water in great numbers either because of their 

 dependence on light, or driven by warm currents in the 

 water, or attracted by some passing mass of food material. 

 The swarmspores germinate, each forming a ue\v plant, as their 

 movement ceases they surround themselves with a cell-wall, 

 grow, and then divide ; in Fig. 6 6, two may be seen in the con- 

 dition of germination, and about to attach themselves by means 

 of the front end, which has been developed into haptera (see also 

 Fig. 5 B, lowest figure). 



FIG. 5. Cludopliora glomerata. A The lower cells are 

 full of swarmspores, whilst from the upper one the 

 greater part have escaped through the aperture m. 

 B Free and germinating swarmspores. 



FIG. 6. (Edoqonium : a 

 (free), b germinating swarm- 

 spores. 



The sexual reproduction here, probably in all cases, con- 

 sists in the coalescence of two masses of protoplasm, that is, in 

 the fusion of their nuclei. 



The simplest and lowest form is termed conjugation, orisoga- 

 mous fertilisation, and is characterized by the fact that the two 

 coalescing cells (termed gametes) are equal, or almost equal, in shape 

 and size (the female gamete in the Cutleriacece, e.<j. Zanardinia 



