Dr. Johnson’s observations on 
344 . 
from Muller, upon this subject, may not be devoid of inte- 
rest. “ Spectaculum singulare praebuit hujus (G. punctata, olim 
H. bioculata) cum limace Planorbis conflictus : liinacem ore 
prehendere molitur hirudo ; ille se quam citissime cum stre- 
pitu ex aeris et aquae subitanea pressione orto testa condit. 
Hirudo oram aperturaa tentare pergit, at Limax insidias sen- 
tiens, seque in domuncula hunc contra hostem minus tutum 
credens, animum capit, egreditur et festinanter ad summum 
vasculi marginem prorependo ex aqua aufugit. Miratu 
dignus Limacis instinctus salutem quaerendi fuga in elemen- 
tum Hirudini contrarium ; 
Omnibus ignotse mortis timor, omnibus hostem 
Praesidiumque datum sentire, et noscere tell 
Vimque modumque sui. 
Paucas tamen post boras, jubente natura, in aquam rursus 
descendere coactus, novo sese periculo obtulit, eique demum 
succubuit.” 
The G. tuberculata , and G. punctata, are oviparous ; the for- 
mer producing about 50, the latter about 20 at a birth. The 
same appearance is observed in these animals as in the H. 
vulgaris, when they deposit their ova, that is, a contraction of 
the body both above and below the abdominal foramen 
(Fig. 8.). There is, however, this difference ; the H. vulgaris 
deposits its ova in a capsule, formed exterior to the body, whilst 
in these animals, the ova are simply excluded, held together 
by some gelatinous matter. From six to twelve ova are de- 
posited at a time. When the whole of the ova are excluded, 
they are received into the abdominal pouch of the parent, 
where th§y constantly remain, until their contents are fully 
evolved. If the ova are removed, and kept in a vessel by 
