A Laboratory Manual for Elementary Zoölogy

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: XL PHYLUM PLATYHELMINTHES A. PLANARIA 1. General appearance and behavior.?Obtain one of the living animals in a watch glass and examine with a hand lens (Hegner, pp. 153-58). Compare form, symmetry, and arrangement of parts with that of Hydra and the frog. Which of these two animals does it most resemble?...
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Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: XL PHYLUM PLATYHELMINTHES A. PLANARIA 1. General appearance and behavior.?Obtain one of the living animals in a watch glass and examine with a hand lens (Hegner, pp. 153-58). Compare form, symmetry, and arrangement of parts with that of Hydra and the frog. Which of these two animals does it most resemble? What type of symmetry does it possess? Does it have anterior and posterior ends? dorsal and ventral surfaces? Is the head better differentiated than in Hydra? On the dorsal surface of the head is placed a pair of eyes, and each side of the head is extended into a blunt contractile lobe, or auricle. Observe the peculiar gliding form of locomotion. To what is it due (.4)? Does the animal exhibit muscular movements also? Do these suggest a better developed muscular system than is present in Hydra? How do the anterior end and auricles behave during locomotion? What does this suggest as to their function? Touch various parts of the animal with a needle and note its behavior and relative sensitivity of different regions. Do you think that Planaria is able to respond more effectively to stimuli and in a greater variety of ways than Hydra ? Make an accurate outline drawing several inches long of the animal. 2. Detailed structure.?Place a small Planaria on a slide and anaesthetize with a few grains of chloretone (.4). After it has become motionless, turn it ventral surface up and cover with a cover glass, pressing gently so as to flatten the animal. If a cover glass is not heavy enough, use a piece of thin slide. The animal must not be crushed. Examine under the low power of the microscope. a) General regions and surface of the body: The narrow clear border of the animal is the ectoderm, the central branching dark brown or gray material is the entoderm, and the lighter b...