GIGANTOCYPRIS MOLLERI 189 



when following small nerves such as shown in Fig. 14. To obtain this the best method 

 is to use some structures, preferably near the edge of the projected image as guides- 

 structures which maybe will not come into the final picture. Thus, muscles running in 

 various directions can be used. To illustrate this I have photographed (Plate XLII) the 

 series of sections from which Figs, ja, b were reconstructed. These figures show the 

 lateral body wall and the underlying pericardial floor. Now these are thin and stain 

 very faintly, and to reconstruct them without the help of some guides would produce 

 a very inaccurate picture. The muscles in the pericardial floor itself were used as such 

 guides, and by comparing the successive sections with Fig. 7 it can be seen how they 

 were used to join the sections together in the projection. 



These photographs and Figs. 7 a, b also illustrate how it is possible in this method 

 to omit any structure in the reconstruction and figure only some underlying structure. 



Another advantage of the method is that the reconstruction can be carried out in 

 either direction. Thus an outer view of the upper lip and surrounding limbs was obtained 

 for Fig. 3, while by reversing the order of projection an inner view of the same region 

 was obtained for Fig. 8. Actually these are from two separate series. 



The sections were stained in Mallory's triple stain or in chlorazol black. 



In addition to the sections several specimens were dissected, and for this purpose 

 they were placed under spirit on a piece of black velvet to produce a good background. 

 It was as a result of this method that chlorazol black was accidentally discovered. It is 

 used in the dyeing of velvet, and minute quantities dissolved in the spirit and stained 

 the chitinous sclerites a dark green. A black solution was therefore extracted from the 

 velvet by boiling with spirit, and through the courtesy of Imperial Chemical Industries 

 its main constituent was identified as chlorazol black (Cannon, 1937). 



SYSTEMATICS 



The genus Gigantocypris was established by Midler (1895) to include five specimens 

 of a giant cypridinid collected during the cruise of S.S. 'Albatross', in an open net, off 

 the west coast of Central America, between 100 and 1700 fathoms. These he called 

 G. agassizii. In 1920 Skogsberg described a new species from relatively abundant 

 material collected "within the region of the Gulf stream" (p. 218) during the North 

 Atlantic Deep Sea Expedition (1910) of the S.S. 'Michael Sars'. This he named 

 G. mulled. The characters on which Skogsberg bases the distinction between the two 

 forms are: 



(1) The length of the shell is greater in G. agassizii. 



(2) The antennule has seven joints in G. agassizii and eight in G. mulleri. 



(3) The second trunk limb has more than 200 cleaning bristles in G. agassizii and 

 up to 140 in G. mulleri. 



(4) The lengths of the joints and the terminal spine of the endopodites of the antenna. 



(5) Short spines are present at the bases of certain of the natatory setae of the 

 exopodite of the antennae in G. mulleri but are absent in G. agassizii. 



