96 SUPPLEMEIVT 



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 

 teutacula, 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 ; from 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 geuera he gave different names, but 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, w^hich have since been adopted by M. de 

 Lamarck, in his New System of Invertebrated Animals. 



