OF THE NERVOUS SYSTEM. 85 



and under surfaces, but the surfaces so named in the annu- 

 lose are morphologically distinct from those similarly desig- 

 nated in the vertebrate animal. The annulose animal moves 

 on the surface which was turned away from the vitellary mass 

 during development ; the vertebrate animal moves on the 

 surface which was applied to it during development. As the 

 axis of the nervous system is formed at the surface turned 

 away from the vitellary mass, and the axis of the vascular 

 system is formed at the surface applied to it in both types of 

 organisation, I employ, as morphological designations, the 

 term neuropod (wugov, vovg) for an annulose, and hsemapod 

 (aTpa, vovg) for a vertebrate animal. 



The mouth of the entomosomatous animal is invariably 

 situated between two somatomes, so that a certain number 

 of somatomes are interposed between it and the anterior 

 termination of the body. As the mouth is only one of a 

 number of openings situated between somatomes, I find such 

 openings conveniently distinguished as metasomatomic. 



The mouth of the neuropod is a neural, that of the hsema- 

 pod a haemal metasomatomic opening. 



As the somatome exhibits in its structure corresponding 

 segments of certain or of all the organic systems, I have found 

 the following morphological terms extremely convenient in 

 referring from the segment of one organic system to the cor- 

 responding segments of the others. 



For the entire framework of an entomosome, whether this 

 framework be developed in its integument or in its interior 

 whether it be fibrous, cartilaginous, or osseous I employ the 

 term sclerome (VxA^g, with the termination of completeness). 

 To a segment of the sclerome I apply the designation sclero- 

 tome (tfxtojgte, refAvu). An aggregate of more or less modified 

 sclerotomes I name a syssderotome (ffuv). Making use of my 

 former illustration, the sclerome of a typical crustacean con- 

 sists of twenty-one sclerotomes grouped in three syssclerotomes. 



