420 Dr. H. J. Hansen on the Morphology of the 
segments of the endopodite of the jaw; in proportion to the 
segments these lateral processes often become extraordinarily 
large, greatly elongated, separated therefrom by an articula- 
tion, and even sometimes transversely divided, in consequence 
of which it is only with difficulty that they can be understood 
when but a superficial examination is made. It is there- 
fore necessary to trace the segments in the endopodite of the 
maxille in thoroughly cleansed preparations, and at the same 
time to find out from which segment the chitinous lamellae of 
the masticating-lobes proceed. ‘This appears to me to be the 
only certain method of procedure, and, if this be done, all the 
secondary modifications of form &c. which take place in the 
masticating-lobes will no longer have a disturbing effect upon 
our conception of the morphology of the structures. 
5. From reasons which the sequel will make readily intelli- 
gible I propose to term the first pair of jaws in Crustacea 
maaillule and the second pair maxille. 
6. ‘The hypopharynx (paragnathi, lower lip, tongue) in 
Crustacea has nothing to do with the appendages; it is a 
median and typically bilobed projection from the sternal 
portion of the head behind the mouth-opening. 
IJ. CRUSTACEA. 
a. ENTOMOSTRACA. 
7. On examining the integument of the sixth appendage of 
an Apus (Lepidurus productus was the particular form I 
studied) after cleansing it with potash it is easy to see that it 
consists of six segments, each of which is provided with a 
lobe ; in the case of the first five the lobes are articulated to 
their respective segments, while the sixth lobe is an immediate 
prolongation of the corresponding segment; the fourth and 
fifth segments, at least on the posterior side of the limb, are 
represented by distinct though small chitinous plates. On 
the anterior side of the limb it may be distinctly seen that 
the exopodite proceeds from the base of the third segment 
and the epipodite from the distal end of the second (¢. $8), 
while the large first segment is devoid of a plate or outgrowth 
on the outer side. In the first pair of appendages the lobes 
of the third to the fifth segments have become very long and 
narrow and are divided into numerous small rings. In the 
eleventh pair of appendages in the female the external ex- 
pansion of the endopodite forms one half and the exopodite 
the other half of the egg-sac; the epipodite is very small, 
although distinct. 
