2,8 DISCOVERY REPORTS 



spirit or formalin in sea water. Also it was almost certainly moribund, when it was pickled, for as 

 Linder (loc. cit. p. 7) points out after quoting Ohlin, it could only swim on its side, a quite unnatural 

 position. Moreover, having obtained for the first time a living specimen of a deep-sea crustacean it is 

 only natural that the scientist would keep it alive as long as possible. Whatever happened, it was during 

 the fixation that the first damage to the specimen occurred. Now spirit and formalin are both slow 

 fixatives and take a considerable time to kill an organism. I have even seen a specimen of the fairy 

 shrimp Chirocephalus placed in the relatively fast fixative Bouin, and after one minute it was still 

 wriggling. During this time the outermost musculature becomes fixed, while the inner muscles still 

 contract. Naturally the result is a distorted specimen. It looks to me as though Linder's specimen, 

 during fixation, became distorted in this way, for in the head region the rostrum, together with the 

 antennules and antennae, appear to have been pulled inwards so as to become completely covered by 

 the carapace. This does not occur in any other nebaliacean. Even in badly damaged specimens of 

 Nebaliopsis, in which the body has become wrenched away from the carapace, the head region appears 

 to remain intact with the antennae and rostrum projecting beyond the edge of the carapace. This is 

 very clearly shown in one of Linder's own specimens (loc. cit. Taf. i , fig. 3), which shows just the same 

 arrangement of these parts as in the photograph I am publishing in this paper as well as in that of my 

 original F2 specimen. 



In addition to this fixation damage I think there must have been slow shrinkage of the whole body 

 relative to the carapace after fixation, for in Ohlin 's sketch the hinder margin of the carapace reached 

 only to the front end of the seventh abdominal segment, while in Linder's photograph taken years later 

 it stretches to the hind end. 



Some deep-sea Crustacea are able to stand a journey up to the top and appear quite normal when 

 caught ; thus Gigantocypris is often collected in numbers from great depths and will swim about actively 

 in bowls of sea water. My own studies of this form (Cannon, 1943) have, I think, demonstrated that 

 these forms are quite unaffected by the enormous reduction of pressure which they undergo in their 

 passage upwards of maybe more than a mile. Nebaliopsis, on the other hand, is now known from a 

 considerable number of specimens, and yet only three are anywhere near perfect. The greater number 

 are completely disrupted. Now Nebaliopsis is a much more delicate form structurally than the robust 

 Gigaiitocypris, but I feel certain that this does not explain the difference between them. Gigantocypris 

 has a firm and substantial outer shell, while that of Nebaliopsis is extremely delicate. But, on the other 

 hand, both have bodies constituted of cells containing living protoplasm and, quite irrespective of their 

 exoskeletons, that protoplasm is in equilibrium under enormous pressure. When they are brought to 

 the surface that pressure is relatively quickly diminished. Now, there can surely be no doubt that this 

 change will produce an immediate disturbance of the equilibrium of the protoplasm. In the majority 

 of cases it is probable that the protoplasm would be unable to readjust itself and so would be precipi- 

 tated, with inevitable death resulting. This is what I consider happens in Nebaliopsis. On the other 

 hand, if the protoplasm can so adjust itself as to remain in equilibrium, then the specimen will appear 

 living and normal at the surface as in the case of Gigantocypris. If my argument is correct, it means that 

 Nebaliopsis collected in deep-sea trawling is normally fixed (but not preserved) soon after leaving the 

 depth at which it occurs. It is fixed, that is, its protoplasm is precipitated, by suddenly reduced 

 pressure. Now this will act on all parts of the body quickly at the same time. Thus, there will be no 

 question of penetration of fixative. The protoplasm of all cells of the body, whether they are deep or 

 superficial makes no difference, will suddenly precipitate. There will be no distorting death struggles- 

 one part of the body still alive pulling against another part already fixed. There will be a sort of shock 

 suddenly immobilizing all parts of the body at the same instant, and the result will be a fixed prepara- 

 tion as nearly like the living form as possible. If, now, such a specimen can finish the journey to the top 



