Table 3.

Model results for the MLR analysis of experiments conducted with populations grown at a light intensity of 1000 fc, i.e. experiment described in §2.1. The notation is as in table 1. Additional symbols are the total number of flagellated cells in colonies N_S, the change Δ of the measured quantity over 8 h in normal medium and Δ + δ in diluted medium. Data analysis takes the form d = d₀ + Σ_i a_iv_i + Σ_i b_iN_S,i, with dummy indicator variables v_i = 0, 1 to take account of nominal factors such as the medium treatment, and a, b and d₀ are parameters of the model. A § marks statistically non-significant terms. Differences between replicated experiments were taken into account as a nominal factor and are not reported. In G. pectorale, we found that colonies with more cells had smaller cells with longer flagella regardless of treatment. In Volvox, we found that colonies with a larger number of flagellated cells N_S had a larger radius R and a larger cell concentration per unit area C. In V. barberi colonies with more cells, somatic cells were smaller. Because V. barberi germ cells perform binary fission, it was not possible to measure the germ cell size accurately.

	d0	Δ	δ	NS	r2	F-ratio
C. reinhardtii
rC (µm)	3.43 ± 0.12	1.46 ± 0.18	−0.36 ± 0.18	—	0.58	29
l (µm)	10.18 ± 0.28	−1.50 ± 0.39	§	—	0.43	16
G. pectorale
rC (µm)	5.58 ± 0.44	0.82 ± 0.25	−0.34 ± 0.16	−0.14 ± 0.06	0.45	21
l (µm)	§	§	§	0.57 ± 0.25	0.17	5
V. carteri
R (µm)	126 ± 8.1	46 ± 5.4	14.6 ± 4.86	0.013 ± 0.003	0.65	41
rG (µm)	23.2 ± 0.53	6.1 ± 0.70	−1.16 ± 0.63	§	0.53	29
rS (µm)	3.81 ± 0.08	0.79 ± 0.10	−0.46 ± 0.09	§	0.58	34
l (µm)	14.28 ± 0.58	3.03 ± 0.77	2.14 ± 0.68	§	0.48	23
C (cells/103 µm2)	3.07 ± 0.56	−2.88 ± 0.37	−0.65 ± 0.33	0.021 ± 0.0002	0.69	48
V. barberi
R (µm)	170 ± 15.0	60 ± 10.5	59.1 ± 11.0	0.009 ± 0.002	0.82	74
rS (µm)	6.11 ± 0.28	1.88 ± 0.20	−0.39 ± 0.21	−0.0003 ± 0.0001	0.82	109
l (µm)	24.80 ± 3.51	5.80 ± 2.46	9.93 ± 2.56	§	0.63	22
C (cells/103 µm2)	4.99 ± 0.93	−3.85 ± 0.65	−1.20 ± 0.57	0.0008 ± 0.0002	0.81	65