526 BIOLOGY. 



it to all parts of the body for the purposes of nutri- 

 tion. But now also the right heart suddenly makes its 

 appearance, which drives the blood into the branchiae 

 for oxygenation. This must doubtless be regarded as a 

 higher development, especially since, as I have shown, in 

 the higher animals as well as in the embryo, the right 

 heart is first perfected subsequently to the left. 



The Conchozoa with a double heart are the Sepiae or 

 Cuttle-fishes. These are in consequence correctly called 

 Cardiac animals, and must be regarded as the funda- 

 mental form of this stage. 



With this completion of the heart other, structural 

 changes, which probably stand in intimate connexion 

 with it, appear. In the Snails indeed a kind of renal 

 organ, or what has been called the calcareous gland 

 in the branchial cavity, has been already shown to 

 exist. Whether the shoulder-gland in the other Mol- 

 lusca belongs also to the members of the present class, 

 may be left undetermined. This kidney, like other 

 vegetative organs, pours out its secretion quite involun- 

 tarily. In the Cuttle-fishes it is, however, combined with 

 an organ, by means of which it can discharge its fluid, 

 or the ink, voluntarily as in the higher animals. The 

 kidney or ink-gland with the ink-sac is therefore charac- 

 teristic likewise of the Sepiae, and admits of our calling 

 these creatures Nephritic or Renal animals. 



At the same time the whole form of the body is altered ; 

 it becomes cylindrical, and is provided upon the ventral 

 aspect with neither a muscular keel nor sole, whereby it 

 might glide or shove itself along ; thus herein also a 

 resemblance is manifested to the higher animals. 



This motionless body is on the contrary endowed 

 with independent organs of locomotion, namely, with 

 fins or arms, which are wanting in the Snails and 

 Bivalve Mollusca. The labour of motion is consequently 

 removed by the organs which minister unto it from the 

 body, and thus we trace another similitude to the higher 

 animals, which transport their body from place to place 

 by wings or feet. These animals can be therefore called 



