ova of the sepia , and those of the vermes testacea. 301 
and only uses the shell of the argonaut, when it occasionally 
gets possession of one. 
Some naturalists, unacquainted with comparative anatomy, 
have asserted that in these eggs they saw the argonaut shell 
partly formed ; they must have mistaken the yelk, which will 
be seen in the drawing to be unusually large, for the new 
shell. 
Explanation of the Plates. 
Plate XIII. 
Fig. 1. The shell of the helix janthina, with the ova in its 
camerated nidus, attached to it; magnified twice in diameter. 
Fig. 2. A portion of the nidus magnified 12 times in diameter. 
Fig, 3. A string of the same nidus magnified 25 times in dia- 
meter. 
Fig. 4. Two of the same ova and one empty chamber, magni- 
fied 50 times in diameter. 
Fig. 5. One of the same ova, and 
Fig. 6. The same slightly bruised, both magnified 50 times in 
diameter. 
Fig. 7. A portion of the camerated nidus, in a dried state, 
belonging to the ova of a univalve from South Carolina, of the 
natural size. 
Plate XIV. 
Fig. 1. The shell of the argonauta, with the ova of the octopus 
deposited in it, magnified twice in diameter. 
Fig. 2. A cluster of the same ova, as they are seen when im- 
mersed in water, magnified 12 times in diameter. 
Fig 3. One of the same ova with its pellicle, magnified 25 
times in diameter. 
Fig. 4. The yelk of the egg. 
Fig. 5- A transversal section of the same. 
Fig. 6 A longitudinal section of the same. The three pre- 
ceding figures are magnified 50 times in diameter. 
Fig. 7. A collapsed egg, as seen when taken out of the water, 
magnified 25 times in diameter. 
