6 



Artificial Production of Spores in Monas 



because of the extreme transparency of its protoplasm, but it eventually becomes 

 granular and develops a flagellum, which appears to originate as a long, delicate pseu- 

 dopod, extending outward from the protoplasm. The Monad formed in this way 

 finally becomes motile and swims away, leaving behind the empty spore or capsule. 

 In some cases the spores are not discharged from the resting cell as soon as they 



a^-^^ are formed, but develop within its walls, so that it is 

 ^^^ possible to find spores in all stages of development, 

 (j^% even the young Monads, within the old resting cell, 



^"'^^ The development of the spores usually occupies from 



two to four days, although in some cases it may be 

 delayed for a much longer time. The Monads 

 formed from the spores are at first spherical, and fig. 5 



swim about with the characteristic revolving move- Young Monads devei- 



„ , . . £ -MT mi n ••11 oped from the spores 



ment or this species or Monas. ihe ceils rapidly within the old cell waU 

 become elongated, however, and within a short time °^ *^® resting cell, 

 are indistinguishable in all respects from the adult organism. 



A few typical experiments will be briefly described, as follows: 

 Experiment I. — On April 11 a culture of Monas was placed in 

 the refrigerator at a temperature of 1° to 4° C. The next day examina- 

 tion showed that all the Monads had formed spherical resting cells 

 Some of these were removed to the temperature of the room, and they 

 immediately developed into the motile form. On April 24 many of 

 the resting cells had broken up into spores. A small number of these 

 resting cells and spores were isolated under the microscope. The rest- 

 ing cells immediately developed into the motile Monads, as before. 

 On April 26 a few of the spores had formed small Monads, but the 

 development did not go very far because of a lack of oxygen in the 

 closed cells which contained the spores. 



Experiment II. — On April 18 a culture of Monas was put on ice at a tempera- 

 ture of 10° C. On May 3 the culture was removed to a temperature of 6° C. A 

 large number of spores had been formed, a large proportion of them remaining within 

 the resting cells. On May 6 many of the spores had developed into young Monads. 

 A large number of the Monads were found swimming about within the walls of the 

 resting cells. 



Experiment III. — On May 14 a culture of Monas was placed on ice at a tempora- 

 ture of 1° C On May 22 a large number of the resting cells and spores were removea 

 to the room temperature and isolated under the microscope in closed cells that contained 

 fresh-water Algae. Development of the spores commenced at once, and on May 25 

 they had reached the motile Monad form. 



FIG. 4 

 Four stages in the 

 development of 

 the spore into the 

 motile Monad. 



76 



