230 “Report of the Microscopical Section. [Sess. 
The Canthocamptus has only one ovisac, which is attached 
to the first segment of the abdomen, and usually contains a 
large number of eggs. From the caudal extremity there issue 
two very long flexible spines with serrated edges, and it is 
from these appendages that the generic name is derived. 
Diaptomus.——The last genus studied was the Diaptomus, 
one of the genera included by Baird in the family Diaptomide, 
but now removed to the family Centropogide, and belonging, 
like the two preceding genera, to the order Copepoda. The 
species chosen was the Diaptomus castor. 
The Diaptomus is a one-eyed animal, the large single eye 
being situate at the anterior extremity of the first segment of 
the body. The shell consists altogether of ten segments, of 
which five belong to the cephalo-thoracic portion and five to — 
the abdomen. The antenne are very large, their length being 
equal to that of the body ; they are divided into a great number 
of articulations, and are furnished with strong sete. 
There are five pairs of legs: the first four pairs much 
resemble the corresponding pairs of the Cyclops, but are much 
longer. ach of these legs consists of two branches springing 
from a common base, and each branch of the second, third, 
and fourth pairs of legs consists of three articulations furnished 
with very fine plumose sete. The terminal sete of the 
branches are very long, and form a beautiful microscopic 
object. The fifth pair of legs is somewhat differently formed. — 
The tail consists of two parts, each terminated by five sete 
finely plumose. In a specimen which was steeped for some 
hours in liquor potasse the outer covering was removed, and 
the skeleton was laid bare, showing in a beautiful manner the 
antenne, legs, and tail. The female has one ovisac of a com- 
paratively large size attached to the abdomen, containing a 
large number of eggs. 
The Diaptomus is a very pretty creature, and its move-— 
ments through the water, especially when it is disturbed, are — 
rapid in the extreme. Its generic name seems to be founded — 
upon this rapidity of motion, being derived from the two 
Greek words signifying “ through ” and “ to fly,” as if it seemed — 
to fly through the water. The words of Jurine in this re- — 
spect may be quoted: “Son port est élégant; sa maniére de~ 
s’élancer dans la liquide est noble et hardie; ses mouvements — 
