54 NEW SPECIES OF HYALINE DAPHNIA 
their internal anatomy, the process of deglutition. mastica- 
tion of food, its progress through the gullet into the stomach, 
the perisaltic movement of the digestive canal, the beating 
of the heart, and the circulation of the blood, are al) visible 
under the microscope. 
The peculiarity of this species is. the enormous 
prolongation of the posterior part of the head. This organ 
occupies fully two-thirds of the body of the insect. A line 
drawn from the point of the beak to the occiput, would 
form with the upward curve, a half-circle. The whole 
body is compressed, more especially its cephalic portion, 
the sides of which are almost in apposition, so that it 
resembles a thin sharp plate growing a little more convex 
at the base of the antenne. The anterior part is pro- 
longed into a sharp curved beak. The body below this 
forms a somewhat obtuse angle. On the dorsal line projects 
a long, serrated shell spine. This is straight, but occasion- 
ally curved, and sometimes the tip is broken off, this has 
been the case in Figure No. 1. 
The representatives of the superior antenne (unless 
these are olfactory sete) are found in two flask-like cells, 
bearing each a bundle of papille, and situated on the 
inferior border of the beak, about one-third from the point. 
The edge of the beak from here to the brain ts thickened, 
probably by nervous structures. 
The second antenne, as in all species of this order, 
are highly developed. The broad, flat, radiating muscles 
which unite them to the inner carapace are very prominent. 
The basal joint is large and rounded. From it proceeds 
two branches, each having three joints, the first being the 
longest. Each extremity is adorned with a serrated collar. 
From the inferior border of each joint droops a filament 
very delicately feathered, the end jcint possessing three 
of similar character. These organs are theic means of 
locomotion. Being of greater specific gravity than water, 
and so compressed, they offer little resistance to the force 
of gravity, and naturally sink to the lower depths, unless 
they actively use the antenne. These organs project 
forward, separated by an angle of about 45 degrees. 
They progress by a series of short jumps. During day- 
light they are usually found in the deeper parts of lakes, 
