On the Occurrence of Mithras paradoxus in England. 4385 
loosely in its mother cell, after them at both ends, so that the 
surfaces formed by the septum occur at the base of the retracted 
extremities of the sac. 
This condition consequently shows that, though the two cells 
concerned in the construction of a septum may, as a rule, not 
be recognizable prior to its thickening, there is no cause to doubt 
the presence of those membranes, which is indeed justly deduced 
from other circumstances. 
The stronger cohesion of the two cell-membranes at their 
extremities indicates a dissimilar chemical constitution in their 
different regions—a circumstance that also obtains among some 
cells of the complex tissues of more highly organized plants. 
From all the foregoing facts it follows without doubt, that the 
folds of the joint-cells of Conferva glomerata, so far as they can 
be certainly recognized, have no connexion with the multiplica- 
tion of cells by fission, and indeed exert no demonstrable direct 
influence upon cell-multiplication. On the contrary, it has been 
ascertained that, in Cladophora, in certain cases, the septa ori- 
ginate by the growth and mutual contact of the membranes of 
free endogenous cells ; and upon this ground we may perhaps be 
justified in explaining, by analogy with other instances, the pro- 
cess of normal septum-formation in this plant, which, on account 
of peculiar complications, cannot generally be recognized with 
the same distinctness. 
[To be continued. | 
XLI.— Notice of the Capture of Mithras paradoxus zn England. 
By Joun Brackwatt, F.L.S. 
In the ‘ Annals. and Magazine of Natural History’ (ser. 3. vol. ix. 
p. 375), I have stated my belief that, on a careful inspection of 
Mithras paradozus, it would be found to be provided with four 
pairs of spinners, and a calamistrum situated on the superior 
surface of the metatarsus of each posterior leg. An oppor- 
tunity of establishing the accuracy of this opinion has recently 
been supplied. by my friend Mr. R. H. Meade, who kindly for- 
warded to me a fine specimen of an adult female of this species 
that had been taken in the lake district of Cumberland, in the 
summer of 1863. The capture of this spider, which is now first 
recorded as indigenous to Britain, is a circumstance of peculiar 
interest ; for, having placed beyond all doubt the fact that it 
possesses eight spinners and calamistra, every difficulty that has 
hitherto been experienced relative to assigning it an appropriate 
position in the systematic arrangement of the Araneidea is 
thereby removed. By its well-marked organic characters, it is 
