soles occidere et redire possunt:
dein mille altera, dein secunda centum,
deinde usque altera mille, deinde centum.
Ovid says that Lesbia was a pseudonym that Catullus gave his beloved (Tristia 2.427-8). According to Apuleius (c.124CE-170), her real name was Clodia (Apol. 10). Later scholars have identified her with a sister of the P. Clodius Pulcher, Cicero’s political rival who came to a bad end.
Several of the poems give the impression that Lesbia was married. The Clodia with whom she is usually identified was married to her dull cousin, Q. Metellus Celer, but caused a scandal by her adulterous affairs.
What kind of genitive is this?
Genitive of value or price. Cf. J&S 69. In Catullus’ day, a Roman Legionary earned 10 asses a day (so common soldiers were NOT well paid!). 
Sextus Pompey bronze as, struck in Sicily 43-36 B.C., obverse:- Laureate head of Janus with features of Pompey the Great, reverse:- Prow of Galley, PIVS above IMP below
Sextus Pompey bronze as, struck in Sicily 43-36 B.C., obverse:- Laureate head of Janus with features of Pompey the Great, reverse:- Prow of Galley, PIVS above IMP belowRoman erotic art tends to emphasize sexual positions over romantic kissing but Catullus and Ovid celebrate locking lips with a passion! 
Polyphemus and Galatea kissing. Fresco from Pompeii, House of the Ancient Hunt (VII, 4, 48). This rare example of a passionate embrace is now in the Gabinetto Segreto in the Museo Archeologico Nazionale, in Naples
Polyphemus and Galatea kissing. Fresco from Pompeii, House of the Ancient Hunt (VII, 4, 48). This rare example of a passionate embrace is now in the Gabinetto Segreto in the Museo Archeologico Nazionale, in Naples What 2 forms are spelled thus?
Future perfect indicative and perfect subjunctive.
The meter requires a long –i- here in the penultimate syllable but the form is nonetheless a future perfect indicative here. By Catullus’ day, the short i of the future perfect was often treated as long for metrical purposes.
The meter requires a long –i- here in the penultimate syllable but the form is nonetheless a future perfect indicative here. By Catullus’ day, the short i of the future perfect was often treated as long for metrical purposes.
What is the verb mood (indicative, imperative, or subjunctive)?
Subjunctive
What constructions pair ne with the subjunctive?
Indirect command (in negative), negative purpose clause, verb of fearing clause, [less commonly: prohibitions, exhortations, jussive phrases (ne plus perfect subjunctive).
Which construction is most likely here?
Negative purpose clause.
Here invidere has the sense to cast the evil eye (or cast spells). Spells were believed to gain power and efficacy if they included precise numbers to help target the object of their magic. 
Medea (1866-68) Frederick Sandys. Medea may have been one the greatest witches of antiquity but her power did not bring her happiness in love.
Medea (1866-68) Frederick Sandys. Medea may have been one the greatest witches of antiquity but her power did not bring her happiness in love.Here we have an example of subjunctive by attraction. Sciat is in subjunctive form because it has been attracted into the same mood as sciamus and possit.