Messrs. Hancock Ernbleton f/a the Anatomy of 95 
introduction of the elongated, conical and pointed penis, fig. 5 «, 
into the small simple channel of the spermatheca, fig. 2 i’ , along 
which we believe it to pass to at least beyond its junction with 
the oviduct, if not quite to the spermatheca itself. The penis, as 
represented in the Plate, is from a specimen preserved in spirits, 
but in the living state this organ is capable of taking a much 
more elongated and attenuated form. 
The way in which fecundation is effected v/ill be understood if 
we now' trace the passage of the ova from the ovary to the external 
orifice : they pass along the oviduct, fig. 2 e, and are detained 
awhile in the dilated and convoluted part of it, /, probably to re- 
ceive some necessar}" investment ; after this they are conducted 
forw'ards to where the testis joins the oviduct at k ; here they are 
subjected first of all to the influence of the seminal fluid of the 
individual itself, for there appears to be little or no doubt that 
the double muscular coating of the testis, c, is capable of driving 
its contents either outw'ardly towards the penis «, or if required, 
inwardly towards the ovdduct e'. Ciliary motion may also assist 
in determining the flow of the seminal fluid in either direction. 
The operation of this self-fecundation being thus accomplished 
in the flrst instance, the ova are secondly conveyed backwards to 
the duct of the spermatheca at I, where they undergo the action 
of the semen injected into that receptacle from another animal 
during the sexual union ; afteiw\ards they are carried into the 
right duct of the mucus-gland at n, which is freely continuous 
with the left duct, and with the common female channel of out- 
let h. 
In the wide ducts of the mucus-gland the ova receive their last 
coating and their peculiar arrangement in it, and lastly they are 
expelled through the female orifice h', the form of the channel 
probably impressing upon the continuous strap or cord of mucus- 
enveloped ova the peculiar form which the spaw n of the different 
species is found to possess. 
It w ill thus be seen that a double impregnation is here pos- 
sible, and indeed more than probable, considering the anatomical 
relation of the parts ; but whether it be in everj" instance essen- 
tial, we are not prepared to state. If the experiments of i\I. Alex, 
de Xordmann related in the ^ ^bmales des Sciences Xaturelles,^ 
3 me serie, tome v. 18415, touching the breeding of Teryipes, which 
w'e consider a member of the genus Eolis, be thought conclusive, 
it may be deemed that self-impregnation is alone requisite. Since 
however copulation is observed to take place among these ani- 
mals frequently and freely, even in confinement in the house, w'e 
have little doubt of the necessity of a double impregnation. 
On a re\dew' of our description of the generative organs in the 
above-mentioned species of EoliSj it appears that these organs 
