404 APPENDIX. No. III. 
have procured from my friend Mr. Les, the Botanist, of Ham- 
mersmith, a portion of a camerated nidus brought from South 
Carolina, containing shells of an univalve not very different 
from the chanks of the East Indies. This nidus is represented 
in the annexed drawing. (Plate XIII. fig. 7.) 
I have also, which is still more satisfactory, seen the camera- 
ted nidus of the helix janthina. This animal not living at the 
bottom of the sea, like the vermes testacea in general, depo- 
sits its ova upon its own shell, if nothing else comes in its way; 
one of the specimens of the shell of the janthina caught in the 
voyage to the Congo, fortunately has the ova so deposited, as 
will be seen in the annexed drawings, made by Mr. Baver, who 
was so pleased with the appearance the parts put on in the field 
of the microscope, that he was desirous of making a representa- 
tation of them. (Pl. XIII. fig. 1, 2, 3, 4,5, 6.) 
In this instance, the ova are single, but in other tribes, seve- 
ral ova are contained in one chamber. In the land snail, the 
eggs have no such nidus. The following observations respect- 
ing them were made in the year 1773, the first year that I was 
initiated in comparative anatomy, under Mr. Hunter. He 
kept snails to ascertain their mode of breeding, and the notes 
that were made at the time in my own hand writing, I now 
copy. 
August 5, 1773. A snail laid its eggs, and covered them 
over with earth; Mr. Honter took one out and examined it; 
the egg was round, its covering strong, and of a white colour, 
with a degree of transparency ; it had no yelk; a small speck 
was observable with a magnifying glass in the transparent 
contents. 
On the 9th no apparent change had taken place. On the 
ith the speck had enlarged, but was too transparent to admit 
