VOLVOCINA 



57 



cuticle composed of some substance which does not give the cellulose 

 reaction. Nutrition saprophytic by means of simple substances (fatty 

 acids, aminoacids, etc.). Syngamy is facultatively hologamy or 

 merogamy, isogamous or anisogamous, according to the age of the 

 gametes. In infusions of decaying animal substances. 



Carter ia (Figs. 35, 36). Differs from Chlamydomonas in having 

 four flagella. It is probably a species of this genus that is symbiotic 

 in the turbellarian Convoluta roscojfensis . 



Fig. 43. Pandorina. From Godwin, a. The adult colony of sixteen similar 

 flagellated zooids, x 200. h, A colony undergoing asexual reproduction, 

 X 450 — each zooid has divided to form a daughter colony which still remains 

 within the parent body. Some of the colonies have already produced flagella, 

 and will shortly break out of the wall which enclosed the parent, b-g, Stages 

 in sexual reproduction — b, Motile gametes, c, Stage immediately after fusion 

 of two gametes, d, Later stage showing flagella withdrawn, e, Later stage 

 showing resting zygote with thickened wall. /, Motile individual produced 

 by the zygote on germination, g. New colony produced by vegetative division 

 of the motile individual. 



Haematococcus ( = Sphaerella, Fig. 42). Differs from Chlamy- 

 domonas in that there is a wide space, traversed by protoplasmic 

 threads, between body and cuticle; several pyrenoids. Much hae- 

 matochrome is often present. Isogamous. Common in collections 

 of rainwater. 



Pandorina (Fig. 43). Spherical, fi:ee-swimming colonies of 16 or 

 32 green pear-shaped zooids, each with the organization of the solitary 

 members of the order, closely pressed together with the narrow end 

 inwards and the flagella outwards. An additional cellulose envelope 

 containing mucilage encloses the whole colony. The colonies are re- 

 produced in two ways: (i) asexually, by the repeated fission of each 



