TWO NEW SPECIES OF ONYCHOPHORA. 517 



bearing segment. Their position is in favour of the view 

 tliat they are crural glands which have passed from the 

 outer to the inner side of the renal organs. This would be 

 possible, because the renal openings on this segment have 

 moved slightly forward, as can be seen from the section 

 represented in fig. 34, which, though passing through the 

 renal opening, is taken in front of the last pair of legs. 

 Their structure, however, is in favour of the view that they 

 are derived from the apodal anal segment, and contain a 

 ccfilomic element, but that their openings have moved both 

 forwards and inwards, and have united together in the mid- 

 ventral line. Of the two views above suggested the latter 

 seems the more probable, because the accessory glands of 

 Eoperipatus and the anal glands of Peripatus would on 

 that view belong to the same somite. 



The next form to be considered is Paraperipatus, in 

 which the glands open dorsally above the anns. In Paraperi- 

 patus the penultimate pair of legs has completely dis- 

 appeared, and the genital segment is apodal. As the 

 development of the " pygidial glands" is unknown, it is not 

 at all certain whether they are crural glands or renal organs 

 which have been modified. Their structure is certainly in 

 favour of the latter view. Again, supposing that the}' are 

 modified renal organs, it is not known whether they are 

 derived from the somite next the genital somite or from the 

 one which follows, namely, the anal somite ; the position of 

 their external opening, however, is in favour of the latter view. 



In all the above forms it is probable that the accessory 

 glands belong to the apodal anal segment — a statement, 

 however, which is far from having been proved. As reo-ards 

 their external openings, there seems to have been a gradual 

 sliifting probably in two directions. If these glands represent 

 renal organs it is only natural that they should have opened 

 at first in the same position as the renal organs. In fact, the 

 position of their openings in P. Nova3-Zealandi?e closely 

 resembles that of the renal organs, and a slight shiftino- for- 

 wards and inwards would produce the condition found in 



