160 Proceedings of the 



Organic Symmetry. On the 23rd of May, M. Dutrochet, a Cor- 

 responding- Member of the Institute, addressed a letter to the 

 Academy, relative to the want of symmetry observed in the internal 

 organs of a great number of animals arrived at their fullest state 

 of developement. He does not agree with Bichat,in supposing this 

 want of symmetry to be an essential character of the organs ; but, 

 on the contrary, agrees with M. Cuvier, that in animajs with long 

 bodies there is an evident symmetry existing, which is still more 

 striking in the foetus during the first periods of its existence : the 

 alimentary canal is then extended in a right line from the mouth 

 to the anus, and is perfectly symmetrical. In the original plan 

 of organization, the symmetry was as perfect internally as it is 

 externally ; and if it be afterwards destroyed, it is by a species 

 of abortion of one of the sides. In the larva of the aquatic 

 salamander, when it first leaves the egg, the alimentary canal is 

 perfectly symmetrical. On its two sides, near the beginning of the 

 intestine, are perceived the liver on the right, and the spleen on the 

 left, forming almost a perfect symmetry, as there is scarcely a per- 

 ceptible difference of size, and the form, as well as the position, is 

 precisely similar. In process of time, however, the left livei\ or 

 spleen, becomes an abortion, and is consequently without functions ; 

 so also in the primitive organization of insects, the biliary organs are 

 symmetrical. Sometimes two symmetrical organs will both become 

 abortions : they will then be useless to the body, serving only as 

 indications of the primitive organization. Such M. Dutrochet sup- 

 poses to be the history of the capsule renales. 



* 



Classification ofLusus Nature. On the 1 1th of April, M. Geoffroy 

 St. Hilaire communicated the substance of a memoir which he had 

 prepared, on the classification of a particular family of lusus naturae, 

 which he considers as forming a regular series of anomalous beings, 

 the fundamental character of which depends on the union of the 

 upper part of the nervous cerebro-spinal system of two individuals 

 in a single system, which is either doubled by the fusion of two 

 complete systems, or single by the combination of two corre- 

 sponding halves. The encephalus is to be considered as composed 

 of four systems of lobes the spinal marrow, the cerebellum, the 

 optic or quadrijumal lobes, and the cerebral lobes. In the family 

 in question, the ventral regions remain distinct ; the two beings are 

 perfectly separate, and subject to the ordinary rules of organiza- 

 tion below the navel, but above it they are united and confounded. 

 The vertebral columns inclined forwards unite beyond the atlas, 

 and each produces half of the cephalic elements which terminate 

 them. The following are the names and characteristics of the four 

 classes into which M. St. Hilaire divides this family: 



1. Deradelphus Cephalic elements double as far as respects the 

 medulla oblongata and the occipital part of the brain (hypertrophie 

 de V occipital). The rest of the head single. 



