EXPLANATION OF THE PLATES. 



Wishing to test the truth of this law in as satis- 

 factory and conclusive a manner as possible, I 

 applied to Professor Owen for a specimen of the 

 Siren or Proteus, animals remarkable for the dimen- 

 sions of their blood discs, and that gentleman kindly 

 placed at my disposal an example of the Meno- 

 branchus lateralis, a member of the same peren- 

 nibranchiate group, and the blood corpuscles of 

 which " are rather larger than those of the Proteus, 

 but not so large as those of the Siren." In this 

 animal I found, as I had anticipated, that the 

 soundness of the law was fully maintained. 



The law announced would doubtless be cited by 

 those physiologists who entertain the idea that all 

 the corpuscular elements of the animal fabric proceed 

 from the red blood disc, as a proof of the truth of 

 their theory, against which, however, I conceive that 

 sound and conclusive arguments may be urged. 



