WITH NOTES ON OTHER SPECIES. 75 



their presence in AcJilya. Hartog ('87) later corroborated his statement for A. 

 polyandra and recurva. I have several times recognized cilia on the zoospores of 

 A. Americana, at the instant of escape, by adding to the water on the slide support- 

 ing the specimen a few drops of a one per cent, solution of osmic acid in water, and 

 then staining in situ with a solution of equal parts fuchsin and methyl violet in strong 

 alcohol. This treatment, recommended by me ('91) in a previous note on the subject, 

 demonstrates the presence of cilia unmistakably. In an exceptionally favorable 

 specimen of A, Americana I have seen the cilia on the living zoospores, both before 

 and after their escape from the sporangium ; and in A. polyandra one can hardl}"" 

 fail to notice the very marked ciliary motion within the sporangium during the escape 

 of the spores. It is not improbable that the zoospores of Aplianomyces are also cili- 

 ate, but this has not been shown, and the genus needs more careful study than it has 

 yet received. 



Sometimes the spores escape with the ciliate end directed forward, but it appears 

 to be much more usual for them to pass out in the reverse position. The first spores 

 to leave do so very rapidly, and are closely crowded together, as though strongly 

 impelled from behind or attracted from before. In the species of Aclilya all the 

 spores press outward in a close column, but in Saprolegnia. there is a gradual 

 decrease in the rapidity of their escape, and the last spores may linger for some 

 seconds or even minutes, swimming aimlessly about, and sometimes never finding 

 the exit. 



The zoospores of Saprolegnia, Leptolegnia, Pythiopsis and Leptomitus escape 

 separately into the water, and swim about freely by means of their forward-pointed cilia. 

 After a short time, vai-ying from a few seconds to fifteen minutes, each spore ceases 

 to move about, but continues for a time longer to whirl and rotate, assuming mean- 

 while a spherical form. Sometimes a few whirls are followed by complete quiet, but 

 often the spore continues to sti'uggle for ten minutes or more, as if in vigorous pro- 

 test against giving up its activity.* Finally, it becomes quite spherical and motion- 

 less, though the cilia may occasionally be seen to wave slowly for a time longer, and 

 then to disappear by degrees, being apparently withdrawn into the protoplasmic 

 mass. The spore now becomes encysted by the secretion of a cellulose wall, and so, 

 for the first time, constitutes a closed cell. Huxley has stated ('82) that the spores 



* A curious phenomenon, calculated to arouse speculation as to the nature of the clianges of relations anil tensions 

 ■which take place while the zoospore is coming to rest, has been observed by me in a spore of an undetermined Sapro- 

 legrda. After swarming normally, the spore had nearly come to rest, though with prolonged and vigorous struggles, 

 when suddenly it burst wiih much force, scattering most of the granular protoplasm lo a considerable distance, and 

 leaving where it had been the nucleus with a small part of the protoplasm. There was, as yet, no trace of a 

 membrane. 



