eye 
1884.] Anatomy and Physiology of the Family Nepide. 365 
cone with the apex directed backward. The filaments of the 
optic nerve are branched at their extremities (Fig. 15); each of 
these branches probably enters a cone. The theory of mosaic 
vision is so generally discussed that no repetition of it is needed 
ere. 
II. Tue Muscurar System. 
To bring an animal into true harmony with its surroundings, 
muscles are necessary to move the body from place to place, so 
that the animal may court agreeable, or favorable conditions, and 
shun disagreeable, or unfavorable conditions. 
No special study of the muscular system of the Nepide has 
been made, but a few points that incidentally appeared during 
dissection are mentioned. 
he most striking mass of muscular tissue is in the meta- and 
mesothorax, the muscles of which are mainly concerned in flight 
and in moving the limbs. The muscles of the legs are well de- 
veloped, and may be studied through the integument if it is scraped 
thin. The elevators and depressors of the beak, and the muscles 
of the beak bristles, are easily demonstrated in the head and in 
the prothorax. The respiratory muscles of the abdomen,and the 
muscles of the pharynx, have already been described. In many 
ame Special provisions for the attachment of muscles are pro- 
vided by means of chitinous processes and chitinous threads. 
The latter are very conspicuous in the prothorax of Ranatra and 
in the retractor muscles of the sete. The chitinous processes 
are found plentifully in the meso- and metathorax, and two prom- 
nent ones are borne on the back of the head. 
_ Conclusion —Even in this cursory view of the family Nepide, 
the adaptation of organism to function is often too obvious to 
Pe eg Notice. The influence of food and surroundings, the two 
a ‘mportant factors in modifying structure, is seen producing 
reat similarity of internal organs, under variable external form. 
The adaptive characters are also very apparent in the raptorial 
‘legs, the beak, the sucking pharynx, the respiratory siphon 
h n many other structures. The general principles of their 
Paysiology is the Same as that of the vertebrates. There is the 
aar conflict between waste and repair, the identical processes of 
Pet food into muscle and nerve, the same general chemistry 
__spiration, etc., etc. They are not endowed with mind, but 
Possess Sufficient nervous sense to meet their requirements, and, 
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