432 F. M. BALFOUR. 



(3) A short terminal portion opening at one extremity into the 

 coiled tube (2) and at the other, as I believe, into the body-cavity. 

 This section becomes very conspicuous in stained preparations by 

 the intensity with which the nuclei of its walls absorb the colour- 

 ing matter. 



The segmental organs of Peripatus, though formed on a type of 

 their own, more nearly resemble those of the Leech than of any 

 other form with which I am acquainted. The annelidan affinities 

 shown by their presence are of some interest. Around the seg- 

 mental organs in the feet are peculiar cells richly supplied with 

 trachese, which appear to me to be similar to the fat bodies in 

 insects. There are two glandular bodies in the feet in addition to 

 the segmental organs. 



The more obvious features of the nervous system have been 

 fully made out by previous observers, who have shown that it 

 consists of large paired supraossophageal ganglia connected with 

 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 organised, 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 case. 



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 gangha 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 papillse. 



(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- to the feet ; and the 

 ganglionic swellings of the two cords are connected together by 

 a pair of commissures containing ganglion cells? The other com- 

 missures connecting the two cords together do not contain ganglion 

 cells. 



The chief feature in which Peripatus was supposed to differ 



1 This was known to Grube, loc. cit. 



2 These nerves were noticed by Milne Edwards, but Grube failed to 

 observe that they were much larger than the nerves given off between the 

 feet. 



' These commissures were perhaps observed by Saenger (loc. it.). 



