PROGRESS IN PROTOZOOLOGY

252 D. L. NANNEY
Table 4
Measures of the size of presumptive opisthe Tetrahymenas from fast exponential growth. Only
the basal bodies were enumerated; the volume and length estimates are based on geometrical extrapolations
Species
Surface Mean
Basal Bodies
Volume
Arbitrary Units
Length
Arbitrary Units
Amicronucleate species
T. pyriformis (A) 362 131 19
T. elliotti (B)
T. furgasoni (C)
317
234*
100
«
18
15
T. Iwoffi (E)
Micronucleate species
282 80 17
T. thermophila (1) 369 136 19
T. americanis (2) 434 188 21
T. borealis (3) 400 160 20
T. hegewischi (5) 352 124 19
T. canadensis (7) 447 200 21
(6)
T. pigmentosa ^
440
418
194
175
T. tropicalis (9) 381 145 20
T. hyperangularis (10) 365 133 19
T. austral is (11) 447 200 21
T. capricornis (12) 481* 231 22
T. sonneborni (13) NA — —
T. nipissingi (14) 391 153 20
N a n n e y et al. (1978).
* indicate extreme values.
I will document the constrained variability of only one additional
gross cellular characteristic, that provided by a recent study of Doerder
et al. (1981) on the DNA content of the macronucleus (Table 6).
This study was not so complete with respect to the species of the
T. pyriformis complex; Doerder's group examined only three amicronucleate
species and five mating species. But they also examined
strains of four other species within the genus. With respect to the variation
within the T. pyriformis complex, we note about the same kind
and degree of quantitative variation observed with basal body numbers.
The smallest species is again T. furgasoni, but the largest species measured
was one of the T. pigmentosa subspecies. The smallest species has
about 1/3-1/4 the DNA content of the largest species.
Even this variability, though not large, may nevertheless be exaggerated.
The macronucleus divides "amitotically", and the products are
only approximately equal (Cleffmann 1974). The dispersion of DNA
content within the clone becomes large, as can be seen from the coeffi-
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21
20