Eggs and Larvae of the Nehu — Tester 
the jar. Loss from this source would not af- 
fect the general conclusions appreciably. 
During the course of each day’s operation, 
there was a steady accumulation of inert 
organic material on the silk of the 100 cm. 
net. It was impossible to remove this either 
by use of the pressute hose or by towing the 
net inside-out between stations. It could be 
removed only by scrubbing the net with a 
brush at the end of the day. This would 
probably cause a small but progressive de- 
crease in efficiency from station to station 
within days. During the first 2 days of Survey 
1, barnacles on the ship’s bottom caused 
small rips in the silk of the 100 cm. net, which 
doubtless decreased its efficiency. These were 
sewn prior to the third day of Survey 1, and 
snagging of the net was henceforth avoided. 
The original old, weak grit gauze was re- 
placed with new for Surveys 3 and 4. 
Apart from towing the nets in an identical 
manner and for exactly the same length of 
time for each haul, no serious attempt at 
quantitative sampling was made. In Survey 
2, meter readings were taken with the 12.3 
cm. net. In Surveys 3 and 4, the meter of the 
12.3 cm. net was towed behind the boat, and 
readings were taken for each haul. However, 
except where indicated, adjusted data are not 
presented because (1) comparable adjust- 
ments are not available for all surveys, (2) the 
adjusted data, where available, do not differ 
greatly from the unadjusted data, and (3) the 
variation between identical hauls at the same 
place from day to day probably would be of 
much greater magnitude than the variation 
induced by slight differences in quantity of 
water strained from haul to haul on the same 
day. 
PHYSICAL AND CHEMICAL DATA 
During each of the main surveys, the tem- 
perature of the surface water at each station 
was recorded to the nearest tenth of a degree 
Centigrade. In addition, for Surveys 2, 3, and 
4, a sample of the surface water at each station 
was taken and later analyzed for chlorinity 
325 
(p.p.m.) by the Mohr method. The data are 
given in Table 1. 
In the interim surveys, temperature, chlor- 
inity, and oxygen determinations were made 
at three depths. The oxygen content (ml./L, 
adjusted to 20° C.) was determined by the 
Winkler method. The data are given in 
Table 2. 
EXAMINATION OF PLANKTON SAMPLES 
The plankton samples were examined un- 
der the binocular microscope by transferring 
the material, a small quantity at a time, to a 
Petri dish. Nehu eggs were removed and 
counted (Tables 3 and 4) according to thtee 
categories, ''normal,” "damaged,” and "ag- 
glutinated,” as defined below. Nehu larvae 
were removed, counted (Tables 5 and 6), and 
measured to the nearest tenth of a millimeter 
by means of a micrometer eyepiece. Standard 
length was defined as the distance from the 
tip of the snout to the end of the vertebral 
column (Table 12). Notes were made on the 
quantity of plankton in each bottle and on 
the relative abundance of the dominant or- 
ganisms. 
As the number of nehu eggs per sample 
was relatively small, the entire sample was 
examined rather than only a known fraction. 
This was a time-consuming procedure, usual- 
ly requiring several man-hours per sample. 
Segregation of the nehu eggs and larvae was 
complicated by the presence of large num- 
bers of chaetognaths and ctenophores which 
had to be teased apart. Despite this difficulty, 
it is believed that the counts include practical- 
ly all nehu eggs and larvae in the samples. 
Usually most of the eggs were "normal” 
in appearance — the developing embryo could 
be seen clearly and was surrounded by a trans- 
parent perivitelline space. In some, classed as 
"damaged,” the inner membrane was rup- 
tured and the yolk and shattered embryo had 
invaded the perivitelline space in varying de- 
gree. Obviously these had suffered mechanical 
injury during capture. In others, classed as 
