FLUSTRA. 17 



diversified, compared with the spherules of the preceding- species, — ascend- 

 ing or descending, avoiding obstacles, or passing around them, diverging 

 in wide excursions from a certain point, and the like. They haunt parti- 

 cular spots and objects. Something like a hair has proved very attractive, 

 engaging several for a long time, as they come successively in contact 

 with it. But the light is especially courted. When many have left their 

 cells, in a darkened position, they are found to have congregated chiefly 

 towards one side more illuminated, and, on turning this side in an oppo- 

 site direction, they find their way again to the light. On treating the 

 preceding great multitude thus, the like ensued ; the whole returned to 

 their position next the light. In these courses their motion is partly 

 gyratory, partly progressive, much resembling that of the Hydrachncc in 

 certain respects, and of the Animalcula infusoria ; or they tumble as mis- 

 shapen masses in the element. 



Their peculiar motions are affected, no doubt, by their peculiar 

 figure. Considerable uniformity predominates among the planulse of 

 many Sertularisc ; but the animals before us are distinguished by great irre- 

 gularity of conformation. Though spherical, or somewhat flattened, to the 

 naked eye, and void of other external organs, they present a number of 

 cilia in rapid action as a constant feature under the microscope. 



It would be vain to attempt precise description of such beings, from 

 the want of definite objects as the type of comparison ; and to assume any 

 one as the standard, it would be a fallacious emblem of the rest. 



When moderately enlarged, no discrepancy of shape is sensible, fig. 4; 

 but it becomes evident on encreasing the magnifying power ; fig. 5. Nor 

 can any thing be more singular and conspicuous than the variety exposed 

 under great amplification. Then, amidst a group of corpuscula, some are 

 nearly spherical, some irregular ovoids, some as if contracted in the middle ; 

 one resembles the union of several, another as if environed by promi- 

 nences, and a third has shewn a projection identically like a person's thumb. 

 Also there is a considerable difference in the intensity of colour. — Fig. 6. 

 The body of these corpuscula is certainly soft and variable. But how- 

 ever irregular the exterior outline, the whole is begirt by cilia. Either 

 the same, or some particular organs, which could never be brought dis- 



VOL. II. c 



