SEE1XC BY All) OF THE LENS 



[2' 



each bough, so that when the muscle 

 of the main trunk contracts, the entire 

 structure is drawn downward, or each 

 branch may contract independently of 

 e\ cry i it her. 



On the tip of each bough, or on that 

 of the single stem, are one or more 

 living animals. Like the leaves on the 

 tree, or the fruit on the branches, these 

 invisible, microscopic creatures live 

 and have their being, laboring in their 

 peculiar way for their food, accepting 

 propitious morsels, rejecting undesir- 

 able fragments, spreading their bodies 

 to the aerating currents, reproducing 

 themselves, dying and melting into 

 nothing so far as we can see, but into 

 something probably as valuable to 

 hiefher bodies as certain lower animals 

 are valuable to us. 



Among- these invisible creatures is 

 one form that is so plentiful in certain 

 places in the water that it may be des- 

 cribed as common, or frequent, or 

 abundant, or by any other term of the 

 kind. It is Epistylis, the "animal on a 

 stem." The animals on the stem live 

 singly, or one or two together on the 

 tip of the branching trunk that, with- 

 out a muscle is rigid immovable; when 

 once attached is fixed in that spot for 

 all the time that is allotted to it. Three 

 such colonies of Epistylis are shown 

 in the accompanying photo-micro- 

 graph, in which the little Epistylis 

 bodies and stem are magnified. 



Each animal body, or zooid, is there 

 shown in its contracted, "still-life" 

 condition. Something has frightened 

 the colon}'. A sudden jarring of the 

 water, a quick slap that splashed the 

 surface, the contact of some roving, 

 comparatively gigantic "animalcule," 

 has terrified the little creatures, and 

 each has shuddered into the elongated, 

 ovate form here shown. When their 

 equanimity shall be restored, they will 

 expand the front into an animated 

 funnel and set in motion the five or 

 six circles of cilia, those vibratile hairs 

 that embellish the border, and that 

 labor pretty continuously for the food 

 supply that is entirely dependent upon 

 the currents that these delicate hairs 

 produce by their rapid whirling. These 

 currents, small and weak as they 

 are, set in toward their bearer and 

 owner, and bring within reach of the 

 oral aperture the minute particles of 

 vegetable matters so welcome to the 

 "animalcule." 



None of these anatomical structures 

 are shown in the photograph. They 

 become visible only to the microscope 

 and even then only when the animal is 

 expanded, and is "feeling pretty good." 



idie narrow, dark, curved hand at 

 the front of each body is the nucleus, 

 the center of the animal's life, the spot 

 that its soul inhabits, or what in it 

 ci >rresp< mds to a soul. 



I hese little creatures are worth see- 

 ing, worth studying, worth a deal of 

 thought, worth more than mere word- 

 can convey. A shallow pond is not 

 water only ; it is not water and weeds 

 ( nly ; it is not water and weeds and 

 fish only. It is alive and quivering. It 

 is trembling and rippling with living, 

 invisible, unimagined, active, sentient 

 things, of which our little Epistylis, 

 our minute "animal on a stem" is 

 only one, but it is an interesting one. 



From a Lover of Microscopic Objec- 

 tives. 

 Philadelphia, Pennsylvania. 



To the Editor : 



I note with pleasure, in the June is- 

 sue of The Guide to Nature, the 

 sketch of Robert B. Tolles, whose 

 memory richly deserves to be kept be- 

 fore all users of the microscope, few 

 of whom know much about him. 



There can be no question that ad- 

 vances in the performance of micro- 

 scope lenses were due more to Charles 

 A. Spencer and Robert B. Tolles than 

 to any other two men that ever lived. 

 This may be said without in any way- 

 reflecting on Lister, Wenham, Abbe 

 and many others that were equally 

 earnest in their efforts. "While Tolles 

 achieved the most brilliant results, he 

 had the advantage of being a pupil of 

 Spencer's, who was entirely self 

 taught. The two names may be justly 

 joined. 



I cannot understand the reference to 

 the invention of a three system lens, 

 as this had long been the usual number 

 in a microscope objective. While the 

 number is of minor importance com- 

 pared with the manner of constructing 

 and uniting them, any credit in this 

 direction should go to Tolles for the 

 devising of a type of four system 

 lenses which has been generally 

 adopted for immersion objectives. 

 The number of Tolles optical inven- 

 tions, which include the achromatic 

 triplet magnifier now so generally 



