360 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
this group of plant cells, so much so that in the vertical taken at Station B (6 fathoms) 
there are only about a tenth as many as in the former instance, which dimunition 
affects the numbers at surface, mid-depth, and bottom in about the same ratio. In 
the same S miles, however, that mark the lessening of Clicetoceros there is a very 
notable increase of the round diatoms which are here classed together as Melosira; 
there are thus at Station B more than ten times as many as were previously obtained 
at A, this increase also affecting surface, mid-depth, and bottom numbers of Melosira 
in about the same ratio. In like manner all the other organisms here estimated (i. e., 
Peridinium, Exuvicellce, Lauderia , Bhizosolenia , Navicula , with the copepods) show at 
B an increase over the quantity at A, this being especially true of the Peridinia and 
JExuvicellce. 
As the ship advances now to Station 0 (8§ fathoms), another distance of 8 miles, 
agaiust the flowing tide, there is again a further diminution, not only of Chcetoceros 
forms, but also of most of the other organisms, except the copepods and the large 
diatoms, Lauderia and Bhizosolenia, which increase at about the same rate for surface, 
mid-depth, and bottom distribution, while it is to be noted that Lauderia becomes 
very abundant at the bottom of this vertical at C.* From 0, however, out to the 
last collecting-point of the day, D, miles, there is a general diminution of all the 
organisms except the copepods, which as regularly increase, until at the close of 
the course the organisms obtained from the given samples of water in the vertical at D 
are much fewer than they were at the outset from A. The Clicetoceros , which was so 
abundant at A, is all but absent at D, while all the other organisms except copepods 
have suffered very marked changes. It is to be noted also that Station D is nearly 
four times as deep as A, that the mean temperature of the water is 4° colder, and that 
the amount of microscopic organic debris in suspension (flocculent, yellow-colored, 
“ amorphous ” matter) at D is relatively very much greater than it was at A. 
In order to express the exact relations which these kinds of organisms bear to 
each other as regards quantity, at the different points studied in this representative 
sectiou, reference is made to plate 68, which is a platting of the relative numbers 
representing each kind of organisms in their distribution at surface, mid-depth, and 
bottom. The plan of platting adopted on plates 68-71 in illustration of the planktonic 
distribution is plain. All the organisms used are placed in separate columns under 
each of the respective stations — A, D, etc. The three collecting points in a vertical — 
i. e., surface, mid-depth, and bottom — are so placed in order at each station, while the 
relative abundance of each of tlie factors may be read by the numerals graduated 
upon the left-hand margin of the plate. The relative quantities of al) the organisms 
are constantly maintained, except that the copepods are a hundred times multiplied 
as compared with the others, as will be explained hereafter, while the quantities of 
Melosira are so great that one-half their relative number is used upon the plates; 
their whole number, however, is given in the tables in the text following. In order 
also that comparisons may be made from the totals of these organisms at the different 
points, the following table is inserted: 
* The large species of Lauderia here referred to are not figured in plates 65 and 66, and Prof. Hamilton 
Smith, of Geneva, N. Y., informs me that it is an unusual if not new species. The same gentleman, 
who has done me the great kindness of studying the tangle of Melosira costata and Cluetoceros found 
at Station A, as above described, says that he has never before seen those forms from American shores, 
and that they have been hitherto regarded as characteristic of Oriental — especially Chinese — waters, 
but that he has detected them in the waters of the Firth of Say, Scotland. 
