REPRODUCTION 141 



component indi\'idiials of a colony may either have protoplasmic 

 connections among them or be grouped within a gelatinous enve- 

 lope if completely separated. Or, in the case of loricate or stalked 

 forms, these exoskeletal structures may become attached to one 

 another. Although varied in appearance, the arrangement and 

 relationship of the component individuals are constant, and this 

 makes the basis for distinguishing the types of protozoan colonies, 

 as follows: 



Catenoid or linear colony. The daughter individuals are at- 

 tached endwise, forming a chain of several individuals. It is of 

 comparatively rare occurrence. Examples : Astomous ciliates such 

 as Radiophrya (Fig. 228), Protoradiophrya (Fig. 228) and dino- 

 fiagellates such as Ceratium, Haplozoon (Fig. 103) and Poly- 

 krikos(Fig. 104). 



Arboroid or dendritic colony. The individuals remain connected 

 with one another in a tree-form. The attachment may be by 

 means of the lorica, stalk or gelatinous secretions. It is a very 

 common colony found in different groups. Examples : Dinobryon 

 (Fig. 87), Hyalobryon (Fig. 87), etc. (connection by lorica); 

 Colacium (Fig. 96), many Peritricha (Figs. 280; 282), etc. (by 

 stalk); Poteriodendron (Fig. 109), Stylobryon (Fig. 119), etc. 

 (by lorica and stalk); Hydrurus (Fig. 88), Spongomonas (Fig. 

 118), Cladomonas (Fig. 118) and Anthophysa (Fig. 119) (by 

 gelatinous secretions). 



Discoid colony. A small number of individuals are arranged in a 

 single plane and grouped together by a gelatinous substance. 

 Examples: Cyclonexis (Fig. 87), Gonium (Fig. 93), Platydorina 

 (Fig. 94), Protospongia (Fig. 108), Bicosoeca (Fig. 109), etc. 



Spheroid colony. The individuals are grouped in a spherical 

 form. Usually enveloped by a distinct gelatinous mass, the com- 

 ponent individuals may possess protoplasmic connections among 

 them. Examples: Uroglena (Fig. 87, c), Uroglenopsis (Fig. 87, d), 

 Volvox (Fig. 93), Pandorina (Fig. 94, /), Eudorina (Fig. 94, h), 

 etc. Such forms as Stephanoon (Fig. 94, a) appear to be inter- 

 mediate between this and the discoid type. The component cells 

 of some spheroid colonies show a distinct differentiation into 

 somatic and reproductive individuals, the latter apparently de- 

 veloping from certain somatic cells during the course of develop- 

 ment. 



The gregaloid colony, which is sometimes spoken of, is a loose 



