Facts are stupid things until brought into connection with some general law. AGASSIZ. No man becomes a proficient in any science who does not transcend system, and gather up new truth for himself in the boundless field of research. DR. A. P. PEABODY. Never ask a question if you can help it; and never let a thing go unknown for the lack of asking a question if you can't help it. — Beecher. He is a thoroughly good naturalist who knows his own parish thoroughly. CHARLES KINGSLEY. STRUCTURAL AND SYSTEMATIC ZOOLOGY CHAPTER I PRACTICAL ZOOLOGY It is very desirable that the student should get as much as possible of his knowledge of zoology from a study of the animals themselves rather than from descriptions. It is of course impracticable as well as undesirable to depend entirely upon this source of information. Nevertheless, the student should be taught how to study specimens, both living and dead. For this reason the following exercises in the practical examination of animal forms have been prepared. They consist mainly of mere suggestions of topics for study, the details being left to the teacher, for it is recognized that if a definite outline to be followed rigidly were offered, it would probably be too elaborate for those schools where only a few weeks can be devoted to the subject, and too meager for the schools in which a longer course is given. The exercises provide for a study of the activities and habits of the living, as well as an examination of the structure of the dead specimen. Every important branch of the animal kingdom is represented by at least one common and easily obtained example. It is suggested that the example be studied before a text lesson is assigned on the group which it represents. In this way the student will have a certain amount of original information which will enable him more clearly to comprehend the description of related forms mentioned in the text. In every case careful drawings should be made of the specimen, and full notes on its habits and structure prepared. The appliances needed are a scalpel and a pair of forceps, both of medium size; a magnifying glass; a compound microscope, if protozoa and other minute. forms are to be studied; and a small board on which larger specimens may be laid for the study of the structure. If alcoholic specimens are to be studied they may be placed for examination in vegetable dishes containing equal parts of alcohol and water to prevent drying of the parts. There should be enough of the mixture to cover the specimen. Specimens which have been preserved in formalin may be examined in water. For more particular descriptions of specimens and methods of work reference may be made to the laboratory manuals and text-books mentioned in the Appendix. INVERTEBRATES Protozoa Amœba Material. More or less uncertainty usually attends every attempt to provide at a given time a supply of amœbas for a laboratory class. Nevertheless, the study of this organism should not on any account be omitted, for from no other one is so much to be learned regarding the fundamental properties of living things. A thorough study of the amoeba forms the basis of all sound biological training. Specimens of amoeba are often to be found in the following places: in the slime on the under side of lily pads and along the stem; in the superficial layer of mud in ponds and slowly flowing streams; in damp moss from sphagnum swamps; in the deposit on the sides of water barrels in greenhouses; in aquaria which have been standing for some time and which contain no crustaceans like Daphnia, Cypris, Cyclops, etc. In case no specimens are obtained from ordinary sources, amoeboid cells may be used instead. These may be found by tearing to pieces the gills of a clam, or a mussel, or by killing a frog, cutting through the skin of the abdomen or leg, and removing a drop of the colorless fluid (lymph). To study the specimen, collect with a pipette a drop of the water supposed to contain amœbas, or a drop of lymph, place it on a glass slide, put on the cover glass, and examine with a low power, 3, 1, or inch objective. Be sure to have some sediment or a hair under the cover glass in order that the weight of the latter may not crush the specimen. Topics for Study. The shape, an irregular outline, changing as the animal moves along (sketch the outline at intervals of one or two minutes, and compare the successive sketches); the motion, note its rate and direction; the change of shape is due very largely to the protrusion of portions of the body substance in the form of blunt processes called pseudopodia (singular, pseudopodium) (Fig. 1, page 57). With a higher power (or inch objective), examine the animal's structure, noting that it is composed mainly of a clear, semifluid substance, protoplasm, in which are embedded numerous granular bodies of various sizes and colors, some recognizable as fragments of vegetable substance, together with, probably, one or more diatoms or other minute organisms. In some part of |