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motive parts of the appendages, diminish in proportion, as 
from the middle of the body, they approach the two extre- 
mities ; and how, in front, the attachment of these two modi- 
fied appendages, rises by little and little, so as to open into 
the first rings of the lateral tentacula, and then of the superior 
tentacula, more or less elongated, according to some local 
cause. He also succeeded in showing that the teeth them- 
selves, in such as are provided with them, are nothing but 
fasciculi of hard setae, approximated together, and analogous 
to those of the other rings of the body. 
This mode of considering the external parts of the nereides, 
naturally conducted M. de Blainville to the attempt of render- 
ing their systematic arrangement more perfect. He proposed 
to divide the nereides into eight subgenera, according to 
characters derived from the presence or absence of teeth, 
from those of the tentacula, and from their number ; lrom the 
form of the mouth, furnished with proboscis or not ; from 
the existence, or absence of gills, from the form of the parts 
of the appendages, and even from the absence or presence of 
the black spots which have been regarded as eyes. To all 
these genera he gave different names, blit at the period to 
which we allude, the defect of materials did not permit him 
to perfect or finish his labours. 
While M. de Blainville was thus occupied in revising the 
genus nereis, M. Savigny was employed in the same manner, 
and as materials were furnished him in great abundance, he 
was enabled much more completely to perform his task, as 
may be seen by consulting his system of annelida, forming 
part of the great work on Egypt, by the French Savans. He 
considered these animals in a much more detailed manner 
than had been done previously to his time, at least as far as 
all the external parts are concerned, and established a great 
number of genera, which have since been adopted by M. de 
Lamarck, in his New System of Invertebrated Animals. 
