, On the Occurrence of Mithras paradoxus in England. 435 



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 in England. 

 By John Blackwall, 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 paradoxus, 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 tine 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 diflSculty 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 



