Mid-water Cheetognatha in the North Atlantic. 335 
submitted to the author for examination had been captured 
by open plankton-nets towed in series at definite depths 
between the surface and a little over two miles. The final 
results of the examination of the material showed that, at 
any rate so far as the Coelenterate fauna was concerned, 
Mr. Murray’s method was very useful, and one which may 
be made to yield valuable results. 
Tt was found that in the nets which had been towed in the 
deeper waters of the Atlantic were several species of Medusz 
and Siphonophora which were absent from all the nets towed 
nearer the surface. Aglantha rosea was abundant in hauls 
from below 1000 fathoms, but only occurred in small numbers 
in the more superficial hauls. 
The object of the present communication is to show that 
the distribution of Chztognatha in the various nets leads us 
to similar conclusions and affords valuable confirmatory 
evidence that the dark intermediate waters of the ocean, into 
which the solar rays do not penetrate, are inhabited by a 
population of Chetognatha which, during the month of 
November at all events, is much denser than the population 
of the upper strata, into which sunlight penetrates. 
In the preparation of the accompanying Table (Pl. XXIV.), 
in which the results of the investigation are summarized, 
the method adopted was to measure the lengths of the 
individuals found in the various hauls separately, and to enter 
the results of a census of individuals grouped according to 
their length in the appropriate places in the Table. 
It is thought that in this way a clearer and more trust- 
worthy representation of one of the elements composing the 
Atlantic meso-plankton will be obtained, and that thus the 
main object of the expedition wili be better served than by 
a more or less imperfect attempt at classifying damaged 
material by taxonomic characters of disputed value. 
Among the species recognized were Dr. G. H. Fowler’s 
new species of Sagitta Whartoni, to which the longest indi- 
vidual (47 millim.) is referable, and which seems therefore 
to be a species characteristic of the Atlantic meso-planktonic 
fauna. Many of the smaller individuals seemed to resemble 
8S. bipunctata. As might have been expected, Spadella 
hamata, Mobius, was taken in great numbers in most of the 
nets, but we are not aware of any previous record of this 
species from so great a depth as 1700 fathoms. 
The chief facts of the distribution of the oceanic Cheeto- 
gnatha, which are clearly indicated in the accompanying 
Table (Pl. XXIV.), are, firstly, that the upper hundred 
fathoms contain but few individuals as compared with the 
