ova of the sepia , and those of the vermes testacea. 299 
of examining the nidus, before I could give it my assent. 
Since that time, I have procured from my friend Mr. Lee, the 
Botanist, of Hammersmith, 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. (PI. XIII. fig. 7.) 
I have also, which is still more satisfactory, seen the came- 
rated nidus of the helix janthina. This animal not living at 
the bottom of the sea, like the vermes testacea in general, 
deposits 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. Bauer, who was so pleased with the appearance the 
parts put on in the field of the microscope, that he was desi- 
rous of making a representation of them. (PI. XIII. fig. 1,2, 
3 , 4 , 5 , 6 .) 
In this instance, the ova are single, but in other tribes, 
several ova are contained in one chamber. In the land snail, 
the eggs have no such nidus. The following observations 
respecting them, were made in the year 1773, the first year 
that I was initiated in comparative anatomy, under Mr. Hun- 
ter. 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. Hunter 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 trans- 
parent contents. 
