148 FEESHWATER ALdM. 



think that a brief description of one of the most remarkable sights we 

 have ever been privileged to witness, taken from notes made at the 

 moment, and illustrated by sketches made from the specimen in question, 

 will prove more than usually interesting. 



"At 12 20 this afternoon, on placing the shde under the microscope, 

 I observed that one of the long filaments was breaking up rapidly into a 

 zig-zag of separate joints, each of which remained attached only at a 

 single point to its neighbour. Placing one cell in the middle of the field, 

 I watched it closely, and observed that the somewhat oval mass of endo- 

 ohrome was gradually leaving the cell-case, though chnging to its base as 

 if reluctant to leave it. At the same time there appeared a very faint 

 transparent membrane across the mouth of the open cell, exactly like a 

 thin soap bubble being blown out of it. This quickly increased in size pari 

 passu with the extrusion of the endochrome. At 12 25 this had com- 

 pletely left the cell and formed a spherical green mass inside the 

 "bubble," in fact an incij)ient zoospore. This now began to move very 

 shghtly, and at one side of it appeared faint traces of ciha waving a very 

 little, suggestive of a piece of machinery just getting started. At 12 30 

 the "bubble" was much blo%vn out, and the ciha active, the 

 zoospore twirhng round for part of a revolution and then stopping, 

 and 80 on. At 12 35 the membrane was more enlarged, and 

 only faintly discernible by very careful illumination. At 12 40 

 the zoospore was hberated ; the ciliated end slightly protruded 

 and transparent ; its motion regular and s\vift. At 12 47 this 

 motion was much diminished, the zoospore slowly creeping round with 

 an irregular motion from left to right. At 12 50 the cihary action 

 had become sluggish, and the endochrome was receding from the cell- 

 wall. The vibration of the ciha gi-adually diminished till 1 1, when it 

 quite suddenly ceased altogether ; at the same moment the whole mass 

 of endochrome was violently convulsed loitli a sort of shuddering movement, 

 and the transparent point was much protruded. By 1 3 the cilia had 

 disappeared, the projection of the point was largely increased, and there 

 is no doubt that if the germination had not been arrested by enclosure in 

 the glass cell, the next stage would have been the formation of a distinct 

 nucleus, and the separation through this into two cells, in fact the first 

 process in the development of a filament like the parent one." 



How enormous is the rate of increase in this plant may be inferred 

 from the fact that in one filament in this specimen, both ends of 

 which were bx-oken, the number of cells stiU remaining was 683. 



It will be seen from Plate 11., Fig. 10, that each zoospore is the 

 product of the endochrome of one cell only. 



The formation of true spores in Qidoyonium is the result of the 

 fertihsation of the contents of certain cells by the entrance through 

 small slits in their margins of spermatozoids ; these being produced 

 either from other cells in the ordinary filaments or othei-wise in small 

 " dwarf male plants," which appear to bo developed from the zoospores 

 above described, and of which numbers may be often seen parasitic upon 

 the larger plants. [Plate 11., Fig. 11.] 



[to be continued.] 



