NEBALIOPSIS 203 



the fifth and sixth pairs are fully developed proportionately to the first, second and 

 third pairs. Claus (1889, p. 34, PI. i, fig. 3) has recorded an identical condition in 

 Nebalia geojfroyi. 



Thiele (1904, p. 24) has suggested that his specimen should be distinguished from the 

 typical form as a variety atlanticci, on the grounds that its rostrum showed a slightly 

 different shape and the exopodites of its pleopods were narrower than those figured by 

 Sars. 



I have examined the original specimen from which Sars drew his figures and cannot 

 see any appreciable difference between its rostrum and that figured by Thiele (1904, 

 PI. 3, fig. 38). In addition, I find that Sars' figure of the third pair of pleopods (1887, 

 PI. 3, fig. 4) is inaccurate. In his figure the ratio of length to breadth of the exopodite is 

 only 2-3:1, while from actual measurement I found it to be 3-2:1. The form of the 

 pleopods agreed closely with both Thiele's figures and with the Discovery specimens. 

 I consider therefore that there is no evidence to justify the establishment of a new 

 variety for the Valdivia specimen. 



With regard to the incomplete Challenger specimen (first on the list, p. 201) it is 

 possible that this may represent a distinct species. The complete animal must have been 

 very large — about half as long again as any other specimen yet found. The carapace is 

 more distinctly corrugated than the normal and is of a pale yellow-brown colour. These 

 characters, however, may well be signs of age, and on them alone it would be unjusti- 

 fiable to establish a new species or variety. 



By studying the undistorted specimen F2 , I have been able to make out the normal 

 arrangement of the limbs and so to deduce something as to the mode of life of Neba- 

 liopsis. 



The specimen, as I received it, was extremely transparent. Ohlin's living specimen 

 was described (Ohlin, p. 59) as "in Leben ganz durchsichtig, glashell.. . .Das einzige, 

 was man von ihm. . .sehen konnte, waren die zwei rotgelblich schimmernden, iiberaus 

 kleinen Augen". This transparency made it very difficult to study. Whatever illumina- 

 tion was used, the light penetrated the tissues so that individual parts were very difficult 

 to distinguish. In addition, in the centre of the body, there was an opaque orange 

 ovoid mass which obscured everything above and below it. I have not been able to 

 settle the exact nature of this mass. It was probably the remains of the ovary. Even- 

 tually I found that by focussing a point source (a 150 C. P. Pointolite) on the edge of the 

 limb I was studying, I was able to light up that part leaving the rest of the animal more 

 or less in the dark. This, for instance, was the only way I could see the edge of the 

 carapace. However, I did not make any real headway until I had the beautiful photo- 

 graphs (Plate XXXII) which I owe entirely to the skill of my colleague. Prof. C. J. Patten. 

 These were taken originally at a magnification of about 1-5, the specimen lying in spirit 

 on a piece of black velvet. The illumination was ordinary north daylight on a fairly dull 

 day. By this method the surface only of the animal has been photographed, as will be 

 seen from the side view where the opaque mass in the centre of the body is practically 

 invisible. Without these photographs I could not have spoken with any certainty as to 



