822 EVENING DISCOURSES. 



resemblance to the pseudopodia of Amoeba. In order to illustrate these artificial 

 imitations a cinematograph film was projected of Gad's experiment. In order 

 to make the oil visible on the clear fluid carmine was rubbed up with the oil. The 

 feeding movements of Amoeba were also shown. Among the most interesting of 

 these is the experiment of Ehumbler, in which a drop of chloroform in water 

 takes in and rolls up within itself a very fine thread of shellac. A similar process 

 occurs in Amoeba Verrucosa when it comes in contact with a green filament of an 

 Alga,, as is described and figured by Leidy. Copies of the original figures of 

 Leidy and Rhumbler were projected on the screen. 



The ciliated group of Protozoa were then considered, special attention being 

 given to Paramoecium — a small, unsymmetrical cigar-shaped animal, just visible 

 to the naked eye, and covered with over 3,500 cilia arranged in oblique rows, 

 the cilia forming about 5 £;yth part of the entire weight of the animal. The cilia 

 propel the animal in the water in which it lives, and as they move backwards with 

 five times the energy they vibrate forward the animal is propelled forward, 

 always, however, in a spiral course having a straight axis, a device which is 

 marvellously effective, and is used by many aquatic animals. As the animal 

 moves forward the cilia around the mouth cause a backward current of water, 

 carrying food to the animal. Thus as it speeds along it can sample the water, 

 take in its food, and do what the best submarines cannot do. It takes in its fuel, 

 water and oxygen, en route, as it navigates the abysses of its pool. On meeting 

 any obstacle in its path it has a wonderfully effective mechanism for avoiding 

 these obstacles, the so-called ' avoiding reaction,' so graphically described by 

 Jennings. It reverses its engines — its cilia — automatically swims backwards, turns 

 to one side, and swims forward in a new direction. This backing-out process may 

 be regarded as a negative reaction. It also shows marked positive reactions 

 collecting in certain areas or in water containing dilute acids, an example of what 

 it called ' Chemotaxis.' By means of films specially prepared by Dr. Comandon 

 the movements of Paramoecium were demonstrated, the film giving a vivid repre- 

 sentation of the wonderful life in the water peopled by Paramoecium and other 

 organisms. Such a result is obtainable by photographing objects on a dark 

 ground, the ultra-microscope being employed. Some other films by Dr. Comandon 

 were shown to illustrate the microscopic flora and fauna of the intestine of a white 

 mouse. A film of a Spirillum which moves by means of iiagella was also shown. 



The work done by cilia was demonstrated by means of a film specially pre- 

 pared for the lecture by Messrs. Gaumont. The lower jaw was removed from the 

 brainless head of a dead frog. On the front part of the palate was placed a large 

 piece of the animal's liver, and on this a flag. The liver and flag were rapidly 

 carried backward right into the gullet. The effect of heat in quickening the motion 

 was demonstrated in the same way. The experiment illustrates what the combined 

 action of thousands on thousands of cilia can do, as well as the importance of 

 their action in removing secretions or other particles from the tubes or channels 

 which they line. If their action is impaired — and it is wholly uninfluenced by 

 the nervous system — or if the cells bearing them are shed, as in bronchitis, then 

 the secretions accumulate in the tubes and block them. By means of a stroboscope 

 an analysis of ciliary motion was projected on the screen to show the movements 

 of the individual cilia and the combined action of the whole. By using a 

 mechanical slide of another type the progressive and rolling movements of Volvox 

 were also projected. 



Passing to fixed ciliated protozoons such as Stentor and Vorticella, their 

 characteristic ciliary movements were shown by means of slides, while a film was 

 used to show the movements of Vorticella and the contractions of its stalk into 

 a spiral by means of the myoids, or primitive contractile filaments that extend 

 from its bell into its stalk. 



Movements of animals by means of undulating membranes were next con- 

 sidered, and those of Trypanosomes were taken as the type. Trypanosomes occur 

 abnormally in the blood of many different animals, from fish to man. A particular 

 form in man's blood and in his cerebro- spinal fluid is the cause of the fatal 

 malady 'sleeping sickness.' Their movements in the blood of a rat were demon- 

 strated by means of a film specially prepared by Dr. Comandon, in which these 

 animals, propelled onwards by their flagellum and undulating membrane, could 

 be seen forcing their way among the blood-corpuscles. 



