Other Pelagic Arthropoda. 
475 - 
Period IV—August 1-4. 
Depths. 
Average. 
Day. 
Night. 
Meters. 
No. 
Per cent. 
1 
No. 
Per cent. 
No. 
Per cent. 
0—3. 
0 
0.0 
0 
0.0 
0 
0.0 
3—6. 
0 
0.0 
0 
0.0 
0 
0.0 
6—9. 
5 
27.8 
7 
46.7 
3 
14.3 
9—12. . 
13 
72.2 
8 
53.3 
18 
85.7 
12—15. 
0 
0.0 
0 
0.0 
0 
0.0 
15-18. 
0 
0.0 
0 
0.0 
0 
0.0- 
Total. 
18 
21 
OTHER PELAGIC ARTHROPODA. 
Four animals, other than those already described, were ob¬ 
tained in considerable numbers during our observations, al¬ 
though they were not numerous enough nor present with 
sufficient regularity to give any clear conclusions as to their 
vertical distribution. The first of these is Diaphanosoma brachy - 
urum Fisch. Scattering individuals of this species were ob¬ 
tained in Period I, the total number being 16, with an average 
of less than 2 for each series of observations. In Period II,. 
109 were taken, giving an average of about 4 to an observa¬ 
tion. In Period III, 276, or an average of nearly 20; and in 
Period IV, 1135 were obtained, giving an average of nearly 100' 
for each set of observations. It is obvious that we have during 
July the beginning of the story of the development of Diaphan¬ 
osoma , and observations made later in the year confirm this 
idea. In August three observations showed a catch of 400 to 
600, and in September the number of Diaphanosoma rose to a 
maximum of more than 1000 per series of observations, and the 
species disappeared in October. The vertical distribution of 
this species follows very closely that of Cyclops and Diaptomus. 
Leptodora hyalina Lillj. was constantly present in our collec¬ 
tions, but in very varying numbers. As stated in the account of 
our methods, all of the individuals belonging to this species were 
counted, and from all of the observations a total of 347 individ¬ 
uals was obtained. This would be an average of about 6 speci- 
