PRODUCTION OF ZOOSPORES IN ULVACE.E. 



321 



point, and begin to grow into clusters or filaments (e), in the manner 

 already described. The walls of the cells which have thus discharged 

 their Endochrome remain as colourless spots on the frond ; some- 

 times these are intermingled with the portions still vegetating in 

 the usual mode ; but sometimes the whole Endochrome of one por- 



Fig. 14S. 



Formation of Zoospores in Pliycoseris gigantea (Ulva latissima): 

 — a, portion of the ordinary frond; b, cells in which the En- 

 dochrome is beginning to break up into segments ; c, cells 

 from the boundary between the coloured and colourless por- 

 tion, some of them containing Zoospores, others being empty ; 

 d, ciliated zoospores, as in active motion ; e, subsequent develop- 

 ment of the zoospores. 



tion of the frond may thus escape in the form of Zoospores, thus 

 leaving behind it nothing but a white flaccid membrane. If the 

 Microscopist who meets with a frond of an Ulva in this condition 

 shoidd examine the line of separation between its green and its 

 coloured portion, he may not improbably meet with cells in the 

 very act of discharging their Zoospores, which ' swarm ' around 

 their points of exit very much in the manner that Animalcules 

 are often seen to do around particular spots of the field of view, 

 and which might easily be taken for true Infusoria ; but on carrying 

 his observations further, he would see that similar bodies are mov- 

 ing vfithin cells a little more remote from the dividing line, and 



Y 



