As at the original creation of the animal kingdom, it was the will of the Supreme Being to begin at the foot of the scale and to terminate with man, who was at its summit, thus making a gradual progress towards the most perfect being it was his will to create, and ending with him: so I think it will best manifest his power and perfections if I endeavour to trace out the footsteps of the Deity in the same direction as he proceeded; and instead of beginning, as is usually done by systematical writers, with the highest grade of animals, if I ascend upwards from the lowest.

Our first inquiry must be what are these lowest animals? And are there any organized bodies that partake of two natures, that are either animal at one period of their existence and vegetable at another, or else are partly animal and partly vegetable? These doubtful forms must be sought for amongst what have been denominated first-plants and first-animals; amongst the former is a certain genus or tribe of plants, which are distinguished not only by their simple structure, but also by an oscillatory movement which seems to connect them, in some degree, with the animal kingdom.