ON THE SPHJ5ROSIRA VOLVOX OF EIIHENBERG. 
229 
the upper surface of the compound disk (fig. 7, a) appears to 
be a little depressed. The lateral concavity of the curved 
protoplasms (7, b ) is in all cases directed inwards. Throughout 
the greater part of its length each protoplasm exhibits the 
same green colour and numerous bright granules that appear 
in its upper surface ; but its lower extremity (fig. 7, c), which 
before movements began was directed towards the centre of 
the parent sphere, is colourless ; and from it is projected appa- 
rently a single cilium (7, e). From their rapid motion I 
found it impossible to count them ; and even when aided by 
tincture of iodine and other reagents the result was equally a 
failure ; but my impression was, and is, that each protoplasm 
bore a single cilium, not two. In this stage of its develop- 
ment, each protoplasm bears the closest possible resemblance 
to an j Euglena — the motile condition of Protococcus pluvialis. 
I am convinced, that if one of the gemmae of Sphcerosira and 
an individual Euglena viridis were placed side by side, they 
would be wholly undistinguishable. By what means the several 
protoplasms were bound together I was unable to ascertain. 
Neither did I succeed in tracing their ultimate condition 
after the Volvocince as a whole disappeared from the jar. As 
already observed, when they began to do so, they vanished 
rapidly, and nothing was left in the water indicative of the 
myriads which it contained a few days before but numerous 
spores, if such they are, of Volvox aureus . When I found that 
this was the case, I visited the pond whence the specimens 
were obtained on May 26. Not one solitary example could be 
found either of Volvox or of Sphcerosira ; neither could I dis- 
cover a trace of Uvella , or of any of its compound allies which 
could be identified as having been developed out of a Sphce- 
rcfsira. A few examples of Euglena longicauda were the only 
moving forms of protoplasm that presented themselves. I then 
turned my attention to the mud at the bottom of the pond, 
collecting its surface-layer by means of a glass tube. Spores 
of Volvox aureus in various conditions were not unfrequent, 
but nothing like the young compound gemmae of Sphcerosira 
were to be seen. There was every reason to conclude that the 
latter were as temporary and fugitive in their nature as the 
young spherical gemmae of the common Volvox , and, like them, 
had wholly passed away. What then are the compound gemmae 
of Sphcerosira ? 
Mr. Carter believes them to be a spermatic form of Volvox , 
each separate Euglenaeform organism being a true sperina- 
tozoid. I confess I see no reason for accepting this deter- 
mination. I have been unable to detect in these objects any 
evidence of sexuality, and am more disposed to conclude, with 
Professor Busk, that Sphcerosira is merely a Volvox in which 
