56 DISCOVERY REPORTS 



on the point of hatching. At this stage the nauplius, enfolded by its swimming appendages in the 

 globular form of the shell itself, appears to fit somewhat loosely inside the shell and there appears to 

 be some little space, far less pronounced, however, than that figured by Ruud (1932), between it and 

 the enveloping capsule. Fraser (1936) states that the nauplius completely fills the egg capsule and it 

 may be, therefore, that the looseness I have described results from some slight shrinkage of the 

 nauplius away from the shell after fixation. In eggs in which naupliar development is far advanced, 

 however, the connection between nauplius and shell is an extremely precarious one, so much so 

 that if eggs in this condition be subjected to unnatural strains artificial rupturing of the shell can 

 readily be induced. At Station 2594, where a very large haul of eggs was obtained, no fewer than 

 1080 empty eggshells were found in the sample, all apparently having become detached from fully 

 developed nauplii, either as a result of jostling in the net or through sudden immersion in the fixative. 



Fraser notes that in general the eggs are opaque and rather densely granular. I have noticed, 

 however, that in the earlier developmental stages there is a certain measure of translucency in trans- 

 mitted light which gives to the egg a characteristic pale golden yellow colour, both translucency and 

 colour being most marked in the unsegmented egg and becoming less marked as segmentation pro- 

 ceeds. In a female that had recently spawned oflF Enderby Land in April 1932, 1 found a few unshed 

 unsegmented eggs still clinging to the almost empty ovary. They were translucent and showed the 

 same pale golden yellow colour typical of the early developmental stages found in the plankton. It is 

 in fully segmented eggs, already beginning to diflferentiate the incipient buds of the naupliar append- 

 ages, that the opacity which Fraser describes is most noticeable. 



I found only nine specimens of the First Nauplius, all, as were the two that Fraser found, from 

 shallow coastal water. Of these one had evidently just been hatched, for it still had the swimming 

 appendages folded about the body in the globular form illustrated by Fraser (1936, Fig. i a), while the 

 others, their limbs being fully extended, had obviously been swimming about freely when caught. 

 In the eight free-swimming specimens the dorsal aspect of the body is more perfectly oval than 

 shown by Fraser (1936, Fig. ib) with just a faint indication of broadening at the posterior end. In 

 colour all present the typical milky or porcelain white appearance characteristic of the egg itself and 

 in length they range from 0-63 to 0-66 mm., the measurements of the First Nauplii Fraser found. 

 I have nothing further to add to Fraser's description, which he remarks is that of a normal First 

 Nauplius. The remarkable scarcity of this stage in the plankton upon which Fraser also comments, 

 is discussed on pp. 98 and 205. 



Though somewhat less pronounced the characteristic whiteness of the egg and First Nauplius 

 persists in the Second Nauplius, in the Metanauplius and up to the Third Calyptopis stage, and 

 this, particularly when these stages are present in mass, renders them quite conspicuous in the 

 samples. 



LABORATORY METHODS 

 In analysing the samples from the vertical nets the larvae were picked out with the unaided eye and 

 identified as to stage under a binocular microscope, small to moderate samples of from one to 300 or 

 400 individuals being counted in their entirety, larger samples fractioned as described by Mackintosh 

 (1934, p. 70). In the larger stramin nets the gatherings of larvae, adolescents and adults often ran to 

 thousands, tens of thousands and even hundred of thousands of individuals and with such samples 

 fractional counting was always necessary. Throughout we used the method described by Mackintosh, 

 in many instances, for the bulkier samples, after pre-fractioning by the jug- or bucket-ful. Samples 

 of the order of from one to 500 or so, in the vast majority of instances were counted and measured 

 outright. 



