320 Agricultural Experiment Station, Ithaca, N. Y. 



cam3ra lucida drawings. After making several sketches of desired 

 objects one zoosporangium was discovered emitting the protoplasmic 

 vesicle preparatory to the differentiation of the zoospores. When 

 the eye first fell upon it the object was in the phase represented by 

 Fig. 18. Soon the protoplasm had all passed through the short 

 tube and was collected in a rounded vesicle at the end. There was 

 a slight differentiation of the protoplasm at the time of the pass- 

 age, but it was little marked. The differentiation became more and 

 more marked showing that the mass was dividing into ten or twelve 

 polygonal bodies. The surface of the forming zoospore next the 

 wall of the vesicle, or the periphery, is the longer, and at the mid- 

 dle of the outer surface of the object there soon appears a de- 

 pression which gives each a curved appearance. This form becomes 

 more and more marked and now movement begins, which first ap- 

 pears as a kneading of the entire mass, and as they become more 

 and more sharply differentiated each young zoospore produces an 

 oscillatory movement with its center nearly stationary, the move- 

 ment of course much restricted by the surrounding vesicle. As 

 they assume more distinctly the curved appearance there is de- 

 veloped from each end of the zoospore a cilium by the lashing of 

 which the movement becomes more violent and results soon in the 

 release of the swarmers when they suddenly dart away. 



The movement is now a complex one. The oscillatory move- 

 ment is more marked with a tendency in many cases to produce 

 figure of 8 cycles, which is combined with a jerky progressive 

 movement in the direction of the longitudinal axis. Frequently 

 when they come in contact with some object larger in size, they 

 simulate to some extent the movements of a paramaecium along 

 some object in the water. 



The form of the mature zoospore is broadly fusoid, inequilatera 

 with pointed ends which terminate in a long cilium. After five to 

 ten minutes the movement of the swarm spores becomes slower 

 and finally it nearly ceases and the body undergoes plastic move- 

 ments resembling somewhat that of an amoeba as represented in 

 Fig. 24:. At first this amoeboid movement is irregular but after a 

 few minutes it assumes a definite character which tends to cut the 

 organism into two parts. This progresses until complete fission 

 results in the formation of two zoospores which are oval in form 

 with the cilium attached directly at the smaller end. 



