442 Mr. J. Blackwall on the Structure, Functions, (Economy, 



4. That as Th. punctata is one of the Protozoa, it most pro- 

 bably has a reproductive stage. 



5. That Th. nucleata might readily be derived from such an 

 alteration in one of the cells of Th. punctata as occurs in the 

 sponge-cells when they go to form the seed-like body, or in the 

 Gregarina-cells when they become " Navicella-sacs." 



6. That Thalassicolla nucleata is essentially similar in struc- 

 ture to Noctiluca. 



Finally, I may be permitted to say, that no one can be more 

 fully conscious than myself of the slender and hypothetical 

 grounds on which some of these conclusions rest. My chief pur- 

 pose has been merely to show the tendency of the evidence now 

 extant as clearly and broadly as possible ; — rather to draw out a 

 brief than to pronounce a judgment. 



The following are the authorities referred to in the text : — 



Von Siebold. Vergleichende Anatomie d. Wirbellosen Thiere, p. 7-25. 



. Ueber einzellige Pflanzen u. Thiere. Siebold und Kblliker's 



Zeitschrift, 1849. 

 "Dujardin. Histoire naturelle des Zoophytes Infusoires. 

 Cohn. Nachtrage zur Naturgeschichte des Protococcus fluviatilis. 



Nova Acta Acad. Nat. Cur. 1850. 



Pineau. Sur le Developpement des Infusoires. Annates des Sciences, 

 1845. 



Stein. Untersuchungen liber die Entwickelung d. Infusorien. Wieg- 

 mann's Archiv, 1849. 



. Ueber die Natur d. Gregarinen. Mutter's Archiv, 1848. 



Kolliker. Ueber die Gattung Gregarina. Siebold und Kblliker's Zeit- 

 schrift, 1848. 



. Das Sonnenthierchen. Ditto. 1849. 



Quatrefages. Observations sur les Noctiluques. Annates des Sci- 

 ences, 1851. 



Hogg. Upon Spongilla. Trans. Linn. Soc. vol. xviii. 



Carter. On Spongilla. Annals of Nat. Hist. 1849. 



XXXV. — A Catalogue of British Spiders, including remarks on 

 their Structure, Functions, (Economy and Systematic Arrange- 

 ment, By John Blackwall, F.L.S. 



[Continued from p. 339.] 



87. Theridion nervosum. 



Theridion nervosum, Walck. Hist. Nat. des Insect. Apt. t. ii. p. 301 ; 



Hahn, Die Arachn. B. ii. p. 48. tab. 58. fig. 133. 



sisyphus, Sund. Vet. Acad. Handl. 1831, p. 115. 



Theridium sisyphus, Koch, Uebers. des Arachn. Syst. erstes Heft, 



p. 8 ; Die Arachn. B. viii. p. 73. tab. 273. fig. 644. 

 Titulus 13, Lister, Hist. Animal. Angl. De Aran. p. 51. tab. 1. fig. 13. 



