GIGANTOCYPRIS MULLERI 223 



NERVOUS SYSTEM 

 GENERAL ACCOUNT 



The account of the nervous system given by Liiders (1909, pp. 33-9) is remarkably 

 complete considering the scarcity of his material. It is, however, a relatively easy 

 dissection to remove the entire nervous system, and this is presumably what Liiders 

 did, but, as a consequence, he overlooked some of the largest and most important 

 nerves. He arranged the nerves extending laterally from the massive nerve ring in 

 groups corresponding to the limbs and so did not discover that among these nerves 

 there are four which run to the shell and adductor muscle. A point more difficult to 

 understand is that he overlooked the very well developed visceral system. 



He remarks (p. 37) on the marked difference between the nervous system of Giganto- 

 cypris and that of other Ostracods. It must be remembered however that, at that date, 

 no nervous system of a Cypridinid had been described in any detail. Actually, the 

 nervous system of Gigantocypris differs little from that of a typical Cypridinid such as 

 I described for Doloria, except in the enlargement of the nerve ring and the larger 

 posterior chain system. The former difference is, of course, a direct consequence of the 

 distended shape and size of Gigantocypris. The latter is a point taken by Liiders to 

 indicate the primitive nature of Gigantocypris. I do not agree with this conclusion, 

 and deal with it later (see p. 228). 



A remarkable character in which Gigantocypris differs from Doloria is that the nerve 

 ring is enclosed in a definite sheath of connective tissue which, while investing the 

 nervous matter closely in the posterior part of the ring, extends a considerable distance 

 away from the actual nerve cells in the anterior part (Liiders, 1909, p. 35). There is 

 thus a marked empty space between the brain proper and its neurilemma. At first 

 sight, both in Liiders' published figure and in my own preparations, I attributed this 

 space to shrinkage resulting maybe from poor fixation or as a consequence of the depth 

 from which the animals were obtained. I soon found, however, that the "Discovery" 

 specimens are exceedingly well fixed and there was no evidence either of distension or 

 collapse. From the complete agreement between Liiders' figure (1909, plate 8, fig. 23) 

 and my photographs (Plate XLI, fig. 2 and Plate XL, fig. 1) and from the constancy of 

 the shape and extent of this space in all my series of sections, I am convinced that this 

 is no artefact but a real space occurring in the living animal. The investing sheath is 

 no delicate membrane but a relatively thick sheet of tissue staining bright orange in 

 Mallory. No trace of it occurs in Doloria. I can suggest no function for it and do not 

 know of any other case in an Arthropod brain. 



At the front end of the brain is a group of five nerves, the points of origin of which 

 are so arranged that one is in front and the other four are arranged in a transverse row. 

 The most anterior nerve runs to the relatively small median portion of the nauplius 

 eye, and soon after passing through the neurilemma swells up into a ganglion. It is not 

 always symmetrically placed as in Fig. 13. It sometimes arises to one side of the median 



