and Laboratory Methods. 1693 



with solar apparatus. An interesting series of experiments exhibits (1) the evo- 

 lution of bubbles of oxygen during starch formation, (2) the effects of heat and 

 slight or severe cold on the physiological activity of plant protoplasm, (3) the 

 iodine test for starch in a plant taken in full vigor of growth, (4) the swelling 

 of starch grains when cooked and their change to a translucent condition, and 

 (5) if common potato is used in the previous experiment, the cellulose walls of 

 the cells which contained the starch grains. 



Turning now to animal types, amcebce give living charts which exhibit all 

 details of structure and motion. Many of the infusoria, both free swimming and 

 colonial forms, exhibit their most interesting peculiarities and are easily manipu- 

 lated. The structure of Spongilla, the currents of water from the oscula, and the 

 contractility of the cells of sponge liesh surrounding the oscula are readily shown 

 with low power objectives. Hydras are never failing objects of interest and 

 instruction in their remarkable variations of shape and motion, their habits of 

 feeding, their modes of reproduction, including all the stages of budding and the 

 detachment of the mature bud, and the swarming spermatozoa in the spermary. 

 Many species of worms are excellent objects, small earthworms especially so. 

 All the coarser anatomical details and the nephridia are visible, the movements 

 of the gizzard and its contents, the peristaltic action of the intestine, and the 

 pulsation of the dorsal vessel and the so-called " hearts." The Arthropoda afford 

 an endless amount of available material including adults and all stages of meta- 

 morphosis, which are easily shown by a series including mosquito's eggs, small 

 and large larvae, pupae, and imago. Respiratory apparatus of various types, the 

 circulation of the blood, the pulsation of the heart, even its valvular action, and 

 the ventral nerve cords and ganglia are among the possibilities in projecting the 

 arthropods of various common species. Small univalve or bivalve mollusks dis- 

 play their characteristic modes of locomotion and the action of the siphons. 

 Large fresh-water clams, when properly prepared, afford a striking exhibition of 

 the heart's systolic and diastolic action and of the instant response of the heart 

 to changed conditions of heat or cold. Among the vertebrates, small fish and 

 tadpoles serve for demonstations of swimming, breathing, feeding and the circula- 

 tion of the blood. Small tree-frogs show their adaptation to their habitat. Live 

 chick embryos, during the earlier stages, exhibit various details, including the 

 pulsation of the heart of a warm-blooded vertebrate. 



Many additional experiments might be cited, which have utiUzed land and 

 fresh-water species, and the adaptability of great numbers of marine species is 

 evident at once. The wide range of organisms and life phenomena, from motile 

 bacteria to the pulsating heart of a warm-blooded vertebrate, to which these 

 methods are adapted, the definite results obtained, and the comparatively small 

 cost of the necessary apparatus, commend living charts to all who are interested 

 in bringing students and popular audiences into the closest possible contact with 

 actual life phenomena as well as its structural forms. A. H. Cole. 



University of Chicago. 



