50 
Henfrey, on some Fresh-water 
The forms presented by this organism are exceedingly varied, 
and nothing can be more beautiful than a number of them 
revolving slowly on their long axes in a drop of water, as 
seen under a power of about 100 diameters.* In the first 
place, the perfect form exhibits two patterns shown in figs. 1 
and 3, and there are minute counterparts to these, remain- 
ing in that state, as in figs. 7 and 9 ; while in the water 
where the species is actively multiplying, all sizes between 
figs. 13 and 14, just emerged from the parent frond, and the 
full grown from figs. 1 and 3, &c., occur. The form with 
32 gonidia results from the cell-division going on one stage 
further than in the form, with 16 ; but this difference is fixed 
during the earliest stages of development, as the form with 16 
(fig. 1) never changes into that with 32 (fig. 3), after it 
has become free from the parent. In the perfect forms the 
gonidia are arranged near the periphery of the frond in circles, 
like the equator and parallels of latitude on a globe, so that 
Pandorina resembles Cohn's Stephanosphcera t more closely 
than any of the other Volvocinece, that having a single equa- 
torial ring of gonidia in its globular frond. Among the 
forms with the isolated gonidia occur others almost equally 
numerous with the gonidia collected together into berry-like 
heaps (figs. 15-20) ; these are smaller than the others, but 
equally varied in dimensions ; their gonidia resemble those of 
the other form ; they appear destined to form the resting spores. 
The gonidia are almost globular ; they have no proper 
membrane, but consist of a gelatinous, granular substance 
which contains a thinner fluid in the centre, as it contracts 
strongly by exosmosis when strong saline solutions are ap- 
plied. There is a large, nucleus-like body (the chlorophyll- 
vesicle of A. Braun) at the posterior end of the gonidium 
(fig. 5), and at the opposite side is a short beak-like process, 
with a colourless space behind it ; the pair of cilia arise here, 
and a little to one side and below these is the reddish-brown 
granule called the ' eye-spot' We have never been able to 
observe a pulsating vacuole, as described by Busk and Cohn 
in Volvox and Gonium. 
The gelatinous frond appears to be perfectly homogenous, 
without any boundary membrane. Iodine and sulphuric acid 
do not colour it blue. It is tolerably resistent, and appears 
solid, as it does not give way or become indented by exter- 
nal pressure, as is the case with the hollow frond of Volvox. 
The fronds are multiplied by the conversion of the gonidia 
* A. Braun says they revolve constantly to the right ; but they change 
the direction constantly. 
t ♦ Annals Nat. Hist.,' 2nd Ser., x., p. 321, &c. 
