COLONIAL PROTOZOA. 



AMONG protozoa are to be found various species which, 

 instead of becoming independent and separating from their 

 fellows at once after division, remain for some time, or per- 

 manently, associated in colonies. The formation of groups 

 or companies was noted in Vorticella. Other vorticella- 

 like animals (Carchesium, Epistylis) may be grouped into 

 permanent, branching, tree-like masses. Gonium, Pandorina, 

 Volvox, are well-known examples of free-swimming colonies. 

 Such forms are especially interesting for they show the be- 

 ginning of differentiation and complexity in a phylum com- 

 prising the simplest organisms. They are further interesting, 

 (a) in suggesting a possible origin of multicellular organisms ; 

 (6) in that their animal or plant affinities are still open to 

 question. 



As a type of these colonial forms Volvox is suggested for 

 study. It may often be collected in the spring or fall from 

 small lakes or ponds containing Riccia, duck-weed and other 

 plants. By stocking jars from the water of ponds where 

 the organisms are found, and maintaining conditions as 

 nearly normal as possible, they may be kept in the labora- 

 tory for several weeks. 



I. Morphology. 



1. Form of Colony. -What is the general shape? Color? 

 If living, note the movements of the colony and determine 

 how it is produced. Of how many kinds of cells is the 



