46 



THE AMERICAN MONTHLY 



[March, 



angles for cutting sections in ribbons.* 

 The screw for elevating the slide and 

 holder is graduated to ^■^-o°'"N about 



1 of an inch, and with a spring click 

 for registermg. The sprmg click can 

 be turned aside when not required. 



The holder for material to be cut 

 has universal motion, so that the speci- 

 men can be adjusted to be cut at any 

 plane. Each movement is independ- 

 ent of the others, and all are so com- 

 bined that the specimen is not raised 

 or lowered in adjusting. For the 

 convenience of using the knife squai"e, 

 or at a right angle to the direction of 

 motion of the knife-carrier, and also 

 for cutting sections in ribbons, the 

 holder is reversible, in which posi- 

 tion the specimen is in about the cen- 

 ter of the slide. There is also the 

 German freezing attachment, with 

 atomizer. 



The base and upright are of ja- 

 panned iron, the other parts of brass, 

 nickel plated. The case is so made 

 that it is not necessary to remove the 

 instrument when operating, as it un- 

 folds and will lie flat on the table. 



Pseudo-C'.vclosis. 



BY SAMUEL LOCKWOOD, PH. D. 



A bottle holding scarcely more 

 than an ounce of water, which is 

 occasionally replenished, has had a 

 place for several months in the full 

 light of my study window. When 

 first placed there it contained a little 

 ooze, which was skimmed from the 

 surface of the mud at the bottom of a 

 field pond. For microscopical uses 

 it IS really a miniature pond, so pro- 

 lific has it proved in the numbers 

 and forms of pond-life, for it teems 

 with protococcus and other algaj of a 

 little higher rank, as well as desmids 

 and diatoms, also rhizopods and infu- 

 soria. 



To-day, Jan. 30th, I took a drop 

 from the surface of the mud and put 

 it under the microscope. A fine Ro- 



* Some authorities claim that for cutting fibrous 

 tissue or hard sections a long sliding cut is prefera- 

 ble, whereas for cellular or soft tissue a cut square 

 across is best. 



tifer vulgaris popped into view. 

 But this attractive object was deserted 

 for another less showy, but more in- 

 teresting on account of a weird-like 

 noveltv of its own. It seemed to be 

 a translucent tube with a stream of 

 minute objects coursing along its 

 entire length. At first sight the semi- 

 transparent body was mistaken for a 

 uni cellular plant, and the streaming 

 bodies for globules of protoplasm. 

 In a word, such was the perfect de- 

 lusion, that the movement was taken 

 for the phenomenon of cvclosis. A 

 Y^j water immersion and B ocular 

 were at last employed. The bluish- 

 green of the moving bodies, denoting 

 phycocrome, ' a mixture of chloro- 

 phyl and phycocyanin,' did not favor 

 the cyclosis view — and the high pow- 

 ers now patiently used swamped the 

 entire hypothesis. The containing 

 body was not a cell, but a minute 

 particle of limpid living gelatine. 

 Whereas the tinier green bodies were 

 hyaline cellules, each one being a 

 uni cellular plant. The movement 

 of these tiny globules was in one 

 direction only. There was no return 

 path to complete the cycloidal track, 

 as in the movement of the protoplas- 

 mic pellets in a growing vegetable 

 cell. 



The conclusion is how patent to 

 all. It was Amoeba dijffluens; yet in 

 the numbers I had seen only this had 

 produced such a delusion. The con- 

 tained bodies were one-celled algcE. 

 As the scene held me almost fasci- 

 nated an entire hour, let me tell what 

 I saw, and in such way that the tyro 

 may go along. 



Our amoeba is very active, pro- 

 gressing with a gliding or flowing 

 motion, as a drop of tallow on a 

 warm glass. True, life is manifestly 

 present, but it is life actuating an 

 infinitesimal speck of amorphcnis pro- 

 toplasm. There is no appearance of 

 organized tissue or fibre. Hence 

 there cannot be anything like muscle. 

 Occasionally may be seen one or two 

 contractile vacuoles — really pulsating 

 vesicles. Let us here premise that 



