A PROCESS OF TEMPORARY CHAIN FORMATION 



BY FRONTONIA. 1 



WALDO SHUMWAY. 



In May of this year, while studying the protozoan fauna of a 

 small pond in the New York Botanical Gardens, the writer 

 observed what appeared to be a chain of four holophrya-like 

 ciliates. A careful search of the culture made during the fol- 

 lowing two weeks revealed about a dozen more such chains before 

 the species disappeared. During this time the writer attempted 

 to obtain a pure culture of these interesting forms, with an idea 

 to studying the nuclear changes involved. Although these 

 attempts were all, ultimately, unsuccessful, it has seemed best 

 to put on record what few facts have been observed. The 

 data here given has been obtained from the study of the living 

 material and some few preparations both in toto and sectioned. 



The following stages in the formation of these chains have 

 been observed; single individuals, two-cell chains and four-cell 

 chains. No chains of three or more than four cells have been 

 observed among the large number (over one hundred and fifty) 

 observed. 



The solitary individual is an exceedingly large (circa 300 

 micra) ovoid holotrichous ciliate, densely pigmented and filled 

 with large alveoli, of some alloplasmic substance which stains 

 deeply with nuclear dyes. The color is dark brown to black 

 with transmitted light and light brown to white with reflected 

 light. The mouth is anterior and lateral with rows of cilia which 

 simulate two undulating membranes. There is a large lateral 

 contracting vacuole. The cortical layer contains trichocysts. 

 The macronucleus is large and oval, the micronuclei have not 

 been observed in my material. The form is an active swimmer 

 in the surface film of a large culture, but when isolated in Syra- 

 cuse watch glasses sinks to the bottom and encysts. Details 

 of this process are given below. 



In cases where the individual neither dies nor encysts after 



1 From the Zoological Laboratory, Columbia University. 



258 



