476 DISCOVERY REPORTS 



sending a branch forwards and a branch backwards. The latter terminates in the lateral 

 part of the nerve ring, after having given a branch to the antennal nucleus. The anterior 

 branch extends forwards as far as the posterior mass of the protocerebral bridge in 

 which it terminates. In addition, it gives rise to a branch which crosses to the other 

 side of the body and terminates in the central body. I could not determine the cell 

 bodies of these fibres. 



Other fibres which I have labelled e,fandg appear comparatively simple, and their 

 position can be seen from Fig. 9. Underneath the cell bodies labelled /in the trito- 

 cerebral commissure there is a bundle of medium-sized fibres extending up to the 

 antennal motor nucleus, but I could not find any cell stations. 



The giant fibre system is undoubtedly, as in other Crustacea in which such a system 

 has been described, a co-ordinating system for linking up the two sides and the various 

 regions of the body. From the fact that the majority of the fibres terminate in the 

 antennal motor nucleus, it appears probable that the system is a special development 

 for correlating the activities of these limbs with the activities of the other parts of the 

 body. The antenna is, of course, immensely more powerful than any other limb, and 

 it is the main, if not the only, swimming limb. Hence it is not surprising that its 

 nervous mechanism should have such an elaborate intercommunication system with 

 the rest of the nervous centres. 



In addition to the giant association fibres there are the giant motor fibres of the 

 antenna. Such fibres have recently been described in detail by Johnson (1924) in 

 Cambariis, but apparently he did not trace them to their termination. In Doloria they 

 can be traced without any doubt to their endings in muscle. If they represent the only 

 motor elements to these muscles, and that seems highly probable, then, as Mr Pantin 

 has pointed out to me, the degree to which the muscles can be stimulated is very much 

 limited. 



SEGMENTAL EXCRETORY ORGANS 



From recent accounts of the Ostracoda, it is clear that the question of the occurrence 

 of segmental excretory organs in the group is still very obscure. Thus Klie (1926, p. 20) 

 states that fresh-water Ostracods possess three pairs of segmental excretory organs. 

 He mentions the antennulary gland which was originally described by Bergold (1910). 

 This I showed in 1925 was not an antennulary gland, as it occurred in the antenna. 

 The antennal gland he describes is the shell gland of the Cyprids and again, in the same 

 paper, I demonstrated that this could not be considered as a segmental organ for the 

 reason that a true antennal gland, having the typical constitution of a segmental excre- 

 tory organ, occurs alongside the shell gland. It is a larval organ and disappears after 

 the fourth larval stage. He correctly describes the maxillary gland which was first fully 

 described by Bergold (1910) and subsequently by myself (1925). 



In a subsequent publication Klie (1929, p. 37) is still more obscure. He describes 

 a gland "zweifellos als Nephridium anzusprechen " opening at the distal end of the 

 stem of the antenna, but unfortunately he does not say in what form this occurs. 



