52 NOTES ON 
of the head is equal to that of the body; but 
when the animal assumes the form shewn in 
Figures 3 and 4 of plate 6 (which are magnified 
in the same proportion as those in plate 5), it is 
much narrower. 
A favourite speculation among philosophers 
is whether the wheel of this animalcule actually 
revolves, or whether it is avisual illusion. Iam 
inclined to believe it is the latter.* Dr. Ehren- 
burgh informs us, that in the Vorticella senta 
the cilia are attached to several globular bodies, 
which are connected to the inside cf the animal 
by slender filaments. 
The form of the eggs is oval; several of them 
are shewn among the green matter at the 
bottom of the drawings. They are sometimes 
of a pink colour, at others of a deep golden 
yellow, with their surface beautifully granulated. 
They are deposited in rows by the parent, and 
may often be seen adhering to the sides of the 
vessels in which they are kept. The best 
method to observe them is to place the bottle 
on a stand. 
The posterior extremity of the body is 
colourless, and furnished with two pair of retrac- 
* See Dr. Faraday’s Observations, in the ‘‘ Journal of the 
Royal Institution.” 
