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APPENDIX. No. III. 



The dlstmguishing characters between the Ova of the Sepia, and 

 those of the Vermes Testa cea, that live in water explained. By 

 Sir EvERAUD Home, Bart. V. P. R. S. 



[From the Philosophical Transaclionstl 



Linnaeus 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 ha^. led before the shell of the ani- 

 mal is formed ; this I have seen taken place in the eggs of the 



