268 Mr Balfour, On certain points [May 19, 



two widely separated ventral cords, — stated by them not to be 

 ganglionated. Grube describes the two cords as falling into one 

 another behind the anus — a feature the presence of which is 

 erroneously denied by Saenger. The lateral cords are united 

 by numerous (5 or 6 for each segment) transverse cords. 



The nervous system would appear at first sight to be very 

 lowly organized, but the new points I believe myself to have made 

 out, as well as certain previously known features in it, appear to 

 me to show that this is not the c?vSe. 



The following is a summary of the fresh points I have observed 

 in the nervous system : 



(1) Immediately underneath the oesophagus the oesophageal 

 commissures dilate and form a pair of ganglia equivalent to the 

 annelidan and arthropodan suboesophageal ganglia. These ganglia 

 are closely approximated and united by 5 or 6 commissures. They 

 give off large nerves to the oral papillae. 



(2) The ventral nerve cords are covered on their ventral side by 

 a thick ganglionic layer*, and at each pair of feet they dilate into 

 a small but distinct ganglionic swelling. From each ganglionic 

 swelling are given off a pair of large nerves"f* to the feet ; and the 

 ganglionic swellings of the two cords are connected together by 

 a pair of commissures containing ganglion cells j. The other com- 

 missures connecting the two cords together do not contain ganglion 

 cells. 



The chief feature in which Peripatus was supposed to differ 

 from normal Arthropod a and Annelida, viz. the absence of ganglia on 

 the ventral commissures, does not really exist. In other particu- 

 lars, as in the amount of nerve cells in the ventral cords and the 

 completeness of the commissural connection between the two cords, 

 etc., the organization of the nervous system of Peripatus ranks 

 distinctly high. The nervous system lies within the circular and 

 longitudinal muscles, and is thus not in proximity with the skin. 

 In this respect also Peripatus shews no signs of a primitive con- 

 dition of the nervous system. A median nerve is given off from 

 the posterior border of the supracesophageal ganglion to the oeso- 

 phagus which j)robably forms a rudimentary sympathetic system, 

 I believe also that I have found traces of a paired sympathetic 

 system. 



The organ doubtfully spoken of by Mr Moseley as a fat body, 

 and by Grube as a lateral canal, is in reality a glandular tube, lined 

 by beautiful columnar cells, which opens by means of a non-glan- 

 dular duct into the mouth. It lies close above the ventral nerve 



■'* This was known to Grube, loc. cit. 



t These nerves were noticed by Milue Edwards, but Grube failed to observe that 

 they were much larger than the nerves given off between the feet. 

 J These commissures were perhaps observed by Saenger {loc. cit. ). 



