[ 402 J : 
APPENDIX. No. IIL. 
The distinguishing characters between the Ova of the Serta, and 
those of the VenrmMES TEstaceEA, that live in water explained, By 
Sir Everarp Home, Bart. V. P. R. 8S. 
[From the Philosophical Transactions, | 
Liyw us was led into an error respecting the animal that forms 
the shell argonauta, by the circumstance of a species of sepia 
having been often found in this shell. This erroneous opinion 
has been adopted by many naturalists upon the Continent, even 
those conversant in comparative anatomy. 
Whether the argonauta is really an internal shell, which I 
have asserted it to be, may possibly never be determined by di- 
rect proofs, as the animal belonging to it has not been met with, 
The present observations are confined to the question of the 
probability of its being formed by the species of sepia frequent- 
ly found in it; and the materials of the present Paper, which 
are furnished from the specimens of natural history collected 
in the late expedition to the Congo, enable me to prove, in con- 
tradiction to such an opinion, that the ova of this particular 
species of sepia are not those of an animal of the order vermes 
testacea, that live in water. 
The young of all oviparous animals, while contained in the 
ovum, must have their blood aerated through its coats, but in 
the vermes testacea, if the shell were formed in the ovum, the 
process of aerating the blood must be very materially interfe- 
red with ; for this reason, the covering or shell of the egg first 
drops off, and the young is hatched before the shell of the ani- 
mal is formed ;_ this I have seen taken place in the eggs of the - 
