334 MM. Audouin and Edwards's Notice respecting 



laws of organization, and that the nervous system, in develop- 

 ing itself, would present modifications similar to those which are 

 met with when it is observed in the series of animals. It 

 therefore became probable that observations made on the same 

 species of crustaceous animal, in its different periods of life, 

 would shew that the nervous system, as it becomes developed, 

 passes through several of the states which we have pointed out 

 in the series of these animals. 



The beautiful researches which M. Rathke has lately pub- 

 lished in Germany respecting the generation of crabs, shew that 

 this is really the case. In these animals, the thoracic nervous 

 system examined in the egg, at first presents two series of gan- 

 glia perfectly distinct from each other, and the number of these 

 pairs of medullary nuclei is then equal to that of the appen- 

 dages, while, in the adult crab, the same ganglia are much less 

 numerous, several having united to form a single nervous mass. 

 Now, this first state of the nervous system of the crab, which in 

 it is only transitory, has a great similarity to that which we have 

 found, but in a permanent manner, in the adult Talitres, which 

 occupy a very low place in the natural series of Crustacea. At 

 a more advanced period of incubation, we find in the egg of the 

 crab the same ganglia already approaching the median line, 

 united together, and forming a single series. This arrange- 

 ment, which is still but transitory, is then comparable to that 

 which is presented by the nervous system of the adult Cymo- 

 thoae. 



The medullary system of the crab afterwards undergoes mo- 

 difications similar to those which we have met with in compar- 

 ing together the Cymothoae, Homards, Palemons, Langoustes, 

 Carcins, and Majee, that is, it undergoes a kind of longitudinal 

 centralization, the ganglia which correspond to the appendages 

 of the mouth approaching each other, and finally forming but a 

 single nervous mass. 



It is therefore seen that in the crab the central nervous sys- 

 tem is developed from the circumference towards the centre, and 

 that it presents, during the foetal life, a series of modifications si- 

 milar to those which we have found in examining the series of 

 Crustacea in the adult state. On afterwards combining M. 

 Rathke's observations with those made by ourselves, we arrive 



