INTRODUCTION. 



Series V. Abnormal conditions of the Osseous and Mus- 

 cular Systems*. 



VI. Abnormal conditions of the Sensory Organs. 

 VII. Abnormal conditions of the Heart and Vessels, 

 VIII. Abnormal conditions of Blood-glands. 

 IX. Abnormal conditions of the Digestive Organs. 

 X. Abnormal conditions of the Urinary and Genera- 

 tive Organs. 

 XI. Abnormal conditions of the Oviduct and Ova of 



Birds f. 



There are many practical reasons why the malformations 

 of each set of organs should be arranged in a separate Series ; 

 it facilitates comparison and reference, and is in accordance 

 with the general plan of arrangement of other parts of this 

 Museum. 



The following considerations on the character and extent 

 of each of the six Classes which have been adopted may be 

 most conveniently discussed in the present portion of this 

 work. 



Class I. VARIATION. 



Syn. Hemiteries, Geoff. 



The term variety is used by naturalists to designate the 

 result of gradually accumulated individual differences, which 

 are themselves slight variations. Some variations are, from 

 their very nature, of a more marked character than ordinary 



* Abnormal conditions of the osseous and muscular systems are so 

 intimately connected with each other that they have been arranged in 

 a single Series. 



f This Series consists of preparations of eggs which are evidently the 

 result of abnormal conditions or functional derangement of the oviduct, 

 and which throw little* or no light upon the more remarkable deviations 

 which occur in the other Series. It may be looked upon as supple- 

 mental to Series X., and it has therefore been placed last in the col- 

 lection. Specimens of abnormal condition of the oviduct have also been 

 arranged in this series, although, in strict conformity with the general 

 plan of the Catalogue, they should have been placed in Series X. : this 

 has been done because they elucidate, in some instances, the condition 

 of the eggs. 



