278 GASTEROPODES. 
at large, I felt more inclined to class them with the Animaleula infusoria, 
than to believe them to be the offspring of sucha parent. In the progeny 
we are disposed to believe there should be some resemblance inherited. 
We are surprised or disappointed if there is none. Even the conviction, 
without the demonstration of metamorphosis, is unsatisfactory. 
It seemed very extraordinary also, that the same product should 
come from the spawn of every different species of Doris which I had an 
opportunity of examining, though the parents bore little reciprocal re- 
semblance. 
After an active but brief existence, all these animalcula perished 
under their primitive form, leaving only a vacant shell. 
This, which is perhaps the most minute shell hitherto observed, 
bears some resemblance to that of the Nautilus, I have named the 
Nautiline, for the purpose of recognition. It is white, and consists of a 
single volute, with a wide surface. Nor could I discover the smallest 
difference in the multiplicity of thousands. Nevertheless, on viewing the 
product while animated, there is the utmost difficulty in determining 
precisely of what it consists. Thus we must not be too confident of spe- 
cifying its form and its parts correctly. 
By lodging specimens of the various species of the Doris in fine 
transparent glass vessels, the observer may casually obtain excellent op- 
portunities of investigating the nature of the spawn if deposited in a 
favourable position. I have had many such in the course of years ; yet 
I have gained less from them than might have been expected. 
The spawn above referred to as deposited on November 11, having 
almost entirely dissolved on December 1, a number of Nautilines, like 
absolute specks in the water, were in great activity. The spawn had 
been pure white, and the same purity distinguished the Nautilines. 
Under the higher powers of the microscope, a general correspondence 
pervaded the appearance of all,—a sac containing several smaller distinct 
viscera, varying somewhat in aspect, according to the view they presented. 
Among them, or in their vicinity, I thought the pulsation of a transpa- 
rent vessel might be discovered. There were altogether two cylinders, 
crowned by long flexible cilia. Behind the roots of the cylinders were 
