9 
Royal Microscopical Society. 
Najas and M. longicornis, the gelatinous basis is deposited in great 
profusion round about the animal, forming a corpulent mass appa- 
rently with no internal integument. But there is evidently some 
connection with the animal and the internal walls of the theca, for 
rapid regressions of the animal always produce an inversion of the 
substance of the theca at the top, but not a coalescence of the mate- 
rial and perfect closing of the top, as Mr. Davis assumes to be the 
case with M. longicornis ; and in these two species the lower por- 
tions are more densely blended with extraneous matters than the 
upper. The substance of the theca of M. Najas is of a very supple 
consistency, for it frequently happens that diatomaceae are involved 
within it, when they are seen to progress and regress in their usual 
manner, although with more difficulty. These two species manifest 
a similitude with the members of the Genus Lacinularia in the 
nature and deposition of the gelatinous basis of the theca. 
In the Genus Lacinularia I place Megalotrocha and Conochilus, 
retaining, however, their specific distinctions for facility of recog- 
nition, as Lacinularia socialis, L. albo-Jlavicans and L. volvox. They 
all arrange themselves in clusters by an attachment of the foot either 
to some vegetable substance or otherwise to each other, as in the 
last instance, L. volvox ; and notwithstanding the evidence that 
exists to the contrary, I beg to submit that the theca of L. albo- 
Jlavicans also becomes blended with foreign particles, similarly with 
the theca of L. socialis, when the animals attain a certain age ; it 
has, as a natural consequence, the ciliated figurum, the same as 
L. socialis ; while in L. volvox, where there is a total absence of 
foreign accessions, the figurum is unciliated. 
I am fully prepared to find the allegation that I here record of 
an inyesting theca in L. albo-Jlavicans disputed, and I can only 
attribute the misconception that has hitherto prevailed on this 
matter, to the supposition that when a theca has been detected it 
has been accepted as L. socialis. A little incident that I here 
relate will confirm such to be possible. In the early part of last 
season Mr. Thomas BGton, of Stourbridge, advertised for the benefit 
of microscopists a supply of Megalotrocha albo-Jlavicans, and being 
somewhat scarce in the neighbourhoods with which I am most 
familiar, I wrote for a supply, and was informed that “ as they had 
all invested themselves in a gelatinous sheath, they must be Lacinu- 
laria.” Mr. Bolton subsequently forwarded me a hand-sketch of an 
individual that he had “ measured up and dimensioned on my 
system,” and an inspection of this showed me at once that it was a 
bona-fide Megalotrocha, according to Ehrenberg’s classification, and 
not Lacinularia, as my friend had been led to assume from the pre- 
sence of the investing theca. 
The points which distinguish the one species from the other are 
very conspicuous, which a glance at Plate XXIII., Figs. 4 and 5, 
