MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 221 
horny layer, also of its own secreting, which sheathes the dart to the end*, guarding 
its extremely fine point, but being open. The elongated pouch lying on the other 
genitalia is, we believe, of a glandular nature, and transmits along its tube or duct 
to the ovate sac its secretion. This fluid is necessarily therefore poured into the 
sheath of the stiletto. Now the pouch into which the stiletto projects, we have 
stated, is capable of undergoing eversion, and when this takes place, the ovate sac 
with the dart becomes thrust into the pouch, and is thus brought to the external 
orifice. This being effected, it is not difficult to conceive that, by successive longitu- 
dinal contractions and relaxations of the ovate sac, the dart may be projected and 
withdrawn by turns, and that the fluid which has been poured into the sheath of the 
dart will of necessity be driven out with the dart, and will therefore inevitably be 
shed into any punctured wound that the dart may have made in the soft body of a 
conjoined Doris. 
The above apparatus is in all probability destined for the inoculation of another 
individual, previous to or during the act of congress, with a fluid of a stimulating or 
aphrodisiac character, the stiletto being analogous to the dart of the common Snail. 
It is perhaps worthy of remark that the penis of Limapontla is pointed with a cry- 
stalline spur-like appendage ; and we may be allowed to make the suggestion, founded 
on this circumstance, and on the above description of the genitalia of D. Johnsioni 
and D. tomentosa, that the twm penis-like organs noticed in OncJiidium by Cuvier in 
his ‘Memoires pour servir,’ &c. as of doubtful character, are, one a penis with a hard 
spur-like end, the other a stiletto, such as has just been described. 
In the latter set of species of Doris there is the same division of the mucus-gland 
into two parts as in the former, but these parts vary somewhat in proportionate size, 
and in the diameter of the tube, which is convoluted in them. 
It will be found, from the foregoing description, that the reproductive organs do 
not differ essentially in Doris from those in Eolis, as given by us in the Annals and 
Magazine of Natural History for February 1848, and hence we infer that the two 
sets of observations and the results drawn from them support each other. At the 
above date we were not aware that Herr Heinrich Meckel had been engaged upon 
the sexual organs of the hermaphrodite Mollusks, as we have since learnt from the 
Report on Zoology for 1844, published by the Ray Society, and we are sorry that it 
has not been in our power to make ourselves acquainted with the full nature of the 
original memoir. From the Report, we find that Meckel takes the same view as 
SiEBOLD, with regard to the organ seated upon the liver, namely, that it is androgy- 
nous, and has the vas deferens included in the oviduct. Since we becarafi ac- 
quainted with the above views, we have examined the generative organs of Helix, 
Limax, Oncliidium and .Aplysia, and it would indeed appear that in these genera the 
part we call testis is insufficient for the function attributed to it ; and in all of them 
we have detected spermatozoa in the ovary, as will shortly be seen we have found to 
* Plate XV. fig. 2. 
