31 



On Certain Points in the Anatomy of Peeipatus 

 Capensis. By F. M. Balfour, M.A., F.H.S.' 



The discovery by Mr. Moseley^ of a tracheal system in Peri- 

 patus must be reckoned as one of the most interesting results 

 obtained by the naturalists of the '' Challenger/^ The discovery 

 clearly proves that the genus Peripatus, which is widely dis- 

 tributed over the globe^ is the persisting remnant of what w^s 

 probably a large group of forms, from which the present tracheate 

 Arthropoda are descended. 



The affinities of Peripatus render any further light on its 

 anatomy a matter of some interest ; and through the kindness of 

 Mr. Moseley I have had an opportunity of making investigations 

 on some well-preserved examples of FeripaUis capensis, a few of 

 the results of which I propose to lay before the Society. 



1 shall confine my observations to three organs. (1) The seg- 

 mental organs, (2) the nervous system, (3) the so-called fat 

 bodies of Mr. Moseley. 



In all the segments of the body, with the exception of the first 

 two or three postoral ones, there are present glandular bodies, 

 apparently equivalent to the segmental organs of Annelids. 



These organs have not completely escaped the attention of pre- 

 vious observers. The anterior of them were noticed by Grube/ 

 but their relations were not made out. By Saenger,* as I gather 

 from Leuckart^s ' Bericht' for the years 1868-9, these structures 

 were also noticed, and they were interpreted as segmental organs. 

 Their external openings were correctly identified. They are not 

 mentioned by Moseley, and no notice of them is to be found in the 

 text-books. The observations of Grube and Saenger seem, in 

 fact, to have been completely forgotten. 



The organs are placed at the bases of the feet in two lateral 

 divisions of the body-cavity shut ofi" from the main central median 

 division of the body-cavity by longitudinal septa of transverse 

 muscles. 



Each fully developed organ consists of three parts : 



(1) A dilated vesicle opening externally at the base of 

 a foot. 



^ Trom the * Proceedings of the Cambridge Philosophical Society.' 



2 " On the Structure and Development of Peripatus Capensis,'' ' Phil. 

 Trans.,' vol. clxiv, 1874. 



3 "Bau von Perip. Edwardsii" * Archiv f. Anat. u. Phys.,' 1853. 

 * " Moskauer Naturforscher Sammlung," * Abth. Zool.,' 1869. 



