SUMMARY 157 



the foremost appendages only are striated, those of the rest of 

 the appendages being unstriped ; it is therefore reasonable to 

 include unstriated muscle in the muscles of this appendicular 

 segmentation and also in the splanchnic segmentation of verte- 

 brates. Moreover in the vertebrate the motor nerve cells of all 

 unstriped muscle have travelled out from the central nervous 

 system to the periphery, so that the motor nerves of such un- 

 striped muscle no longer form part of ventral or lateral roots ; 

 their original segmental position is nevertheless indicated by the 

 outflows of connector fibres which connect these peripheral cells 

 with cells in the central nervous system. Therefore, just as the 

 ventral and lateral roots indicate the somatic and splanchnic 

 segmentation of the voluntary muscular system, so also the same 

 roots will indicate by means of the connector nerves the somatic 

 and splanchnic segmentation of the involuntary nervous system. 

 The thoracico-lumbar outflow of connector fibres is found in all 

 the anterior roots of that region, showing that the dermal mus- 

 culature belongs to the same somatic segmentation as the longi- 

 tudinal striated muscles of the body. The bulbar outflow of 

 connector fibres on the other hand is found in the lateral roots 

 of the bulbar region, showing that the endodermal musculature 

 belongs to the same splanchnic segmentation as the striated 

 branchial and visceral muscles, which arose from the striated 

 muscles of appendages ; the endodermal muscles arose therefore 

 from unstriated appendicular muscles. 



In this way the whole musculature of the new gut receives a 

 uniform explanation up to the end of the small intestine, and at 

 the same time a similar explanation is given for the differences 

 between the somatic and splanchnic segmentation. As previously 

 mentioned, all new segments formed after the establishment of 

 the vertebrate stage would be somatic segments ; owing to the 

 cessation of the formation of appendages no new splanchnic seg- 

 ments would be formed. In the vertebrate body the somatic 

 segmentation both for the unstriped as well as the striated 

 muscles would thus be manifest throughout its whole length; 

 this is clearly the case, for the lateral chain of the sympathetic 

 supplies segmentally motor nerved to the dermal muscles just as 

 the ventral roots supply motor nerves segmentally to the longi- 

 tudinal muscles of the body. On the other hand the splanchnic 

 segmentation would be confined to the head region of the body, 



