LIFE HISTORY OF TWO RARE CILIATES 351 



City College from Van Cortlandt Park. Through the kindness 

 of Dr.Goldfarb, some of the culture was sent to Professor Calk- 

 ins who identified the form as Spathidium spathula. Because 

 of its rarity, the peculiar and interesting nuclear changes shown, 

 Professor Calkins suggested that I make a study of its mor- 

 phological characteristics, its habits, reproductive phenomena, 

 response to stimuli and the processes occurring in its life-his- 

 tory. I wish to express my gratitude to Professor Calkins for 

 his interest in my work and for his helpful suggestions and criti- 

 cisms. 



Before the material came into my hands. Professor Calkins 

 had kept it under observation for a week or more, experimenting 

 with various food-media; he found that Spathidium was ex- 

 tremely sensitive to old bacteria infusions. Although Maupas 

 states that Spathidium captures and eats all kinds of small 

 ciliates, as for example, Cyclidium and Glaucoma, during the 

 entire time I had it under observation, I never saw it paralyze 

 or eat any ciliate except Colpidium, in fact it seems impossible 

 to cultivate it without the aid of this particular form. From 

 time to time during the past five months, I have found in the 

 original culture containing no Colpidia, a few abnormally small 

 Spathidia. That the organisms were not in a healthy condition 

 was shown by their greatly reduced size and the perfectly trans- 

 parent condition of the protoplasm. I am at a loss to account 

 for the free-swimming individuals in the old culture; it may be, 

 however, that some shght change in the environment proved 

 sufficient to cause the emergence of the encysted forms. 



In the rich cultures under observation during the first six 

 months of 1911, if for any reason Colpidium became reduced 

 in numbers, Spathidium encysted. It was quite possible to 

 recover them within four or five hours by adding to the medium 

 containing the cysts, fresh hay-infusion either with or without 

 an abundance of Colpidium. A jar containing the original cul- 

 ture was left tightly covered from January 1 to January 12, 

 1912, upon which date it was examined. Cysts were abundant 

 but no free-swimming forms. A small quantity of fresh hay- 

 infusion was added and the jar was left uncovered. On January 



