84 ON THE MORPHOLOGICAL RELATIONS 



nomenclature. All terms involving more or less than their 

 morphological application demands, must be avoided. Terms 

 derived from other departments of the science, and having 

 therefore an established technical meaning, have invariably 

 produced misconception, when transferred for morphological 

 purposes. 



Influenced by these considerations, and satisfied that the 

 annulose and vertebrate types of organisation, although 

 fundamentally distinct, present parallel forms of structure, 

 and must consequently be closely linked together in morpho- 

 logical inquiry, I have to suggest a more extended and pre- 

 cise system of nomenclature for this department of the 

 science. 



In the annulose and vertebrate types of organisation, the 

 body of the animal consists of a linear ^3 133 of segments. To 

 the constituent segment, with its diveig' '<* appendages, I 

 apply the term somatome (rf/Aa, repvu). 



For the purpose of avoiding circumlocution, and of sup- 

 plying a term for a generalised conception, and thereby facili- 

 tating morphological description, without encroaching on 

 zoological nomenclature, I denominate a segmented animal, 

 whether annulose or vertebrate, an entomosome an entomo- 

 somatous animal (gVo//,os, <rw,aa). 



As the constituent somatomes are invariably arranged in 

 groups, in each of which they are more or less modified in 

 form, or fused together, I find syssomatome (<rt>, <rcD/-c, ripvu) a 

 convenient designation for such a group. A typical crusta- 

 cean presents a cephalic, a thoracic, and a caudal syssoma- 

 tome, in each of which there are seven somatomes twenty- 

 one in all. 



The constituent somatomes lie in planes at right angles to 

 the morphological axis of the body, and are symmetrical in the 

 transverse, but unsymmetrical in the perpendicular direction. 

 They are, however, not only unsymmetrical in their upper 



