JJ4 



KNOW i.i:i)C,i;. 



Ski'tkmhhr. 1912. 



the normal form dies at a tempcratwii- iKtwccn 

 52"C and 55"C, while the contents of the sac 



O formed by the conjii;;ation of 

 two forms withstood a tem- 

 perature of 120'' C for live 

 minutes. This second method 

 of re|)roduction does not in all 

 cases appear to be truly aniso- 

 ,1,'amic, for often the two 

 conjugating gametes appear 

 to lie similar. In other cases 

 liciKi: .!()(). the gametes may differ in 



Normal free-swimininK some respects— generally, one 

 form. is larger and more granular 



than the other. In the forms 

 where holo/oic nutrition is met with, a digestive 

 juice of an acid nature appears to be secreted. 

 In the Moiias sarc()pliaf>a, which habitually ingests 

 other monads, as well as bacteria, I have shown 

 that bacilli stained with blue litmus are almost 

 instantly turned red after ingestion. In this par- 

 ^^^^^ ticular organism this secretion 



^^^^^^^^ appears to act with 

 ^^^^t^B^^ >'a|Mdity, the edges 

 ^^^^H^m^^^^k ingested organism 

 ^^^K^. ^^H^H speedily corroded, till 

 ^^^H' •,' .^^^^^B of undissolved 



FlGL'Ki-; J6I. 



Structure. 



First stage in repro- The structure of the monads 



dnction by fission. is simple. They do not appear 

 to be divisible into an ecto- 

 plasm and an cndoplasm, like the Amoeba. The 

 organism usually consists of transparent protoplasm, 

 with granules embedded therein. Some of these 

 granules are probably of a fatty nature, staining 

 black with osmic acid. All the monads possess a 

 nucleus, which is at times specially prominent. 

 Even in the holozoic forms no mouth opening or 

 anus is present, but in some species food particles 

 are ingested at certain fixed points, usually at the 

 base of the flagella, whilst undigested matter max 



Obe expelled from an\- point 

 in the bod\-, but usually from 

 the opposite end to the 

 MicTiioDs OF Study. 

 A few words on the methods 

 adopted in the study of these 

 organisms may be useful. The 

 Figure .362. microscope used for this class 



Second stage in repro- ^^ ^^'"'"'^ "lust be a firstrate 

 duction by fission. one. It should have a tripod 



foot, and be perfectly steady 

 in any position. A mechanical stage and compound 

 substage are absolutely necessar\-. The microscope 

 that I have used exclusivel}' for my researches on 

 these organisms is one of Messrs. Watson's instru- 

 ments, and although it has been in daily use for over 



four years 1 have not found it necessary to make the 

 slightest adjustment. With regard to lenses, these 

 neetl not be numerous. The 

 objectives I ha\'e found to be of 

 most utility are the half-inch, 

 one-sixth inch, and one-tenth 

 inch dry, and one-twelfth inch 

 homogeneous immersion. A 

 high-powered dry lens is 

 essential for a large part of 

 this work, as an immersion lens 

 is objectionable when following 1 igukl JW. 



a rapidly swimmiiig organism j^^^^ ^^^^^ in "repro- 

 k)r many hours. The one-tenth dnction by fission, 

 inch dry lens that I have used 



for some time was made by Watson's, and is an 

 excellent lens for this work, possessing the three 

 necessary requisites, viz., excellent definition, capa- 

 bility of bearing a large solid cone from a good 

 condenser, and ability to take high e\epiecing. The 

 condenser used should be an achromatic one. the 

 Abbe Illuminator being useless 

 for critical work. The first 

 recjuisite is some means of 

 keeping a minute drop of fluid, 

 containing the organisms, con- 

 tinually moist, and to prevent 

 evaporation. Perhaps one of 

 the best means is that devised 

 by the late Dr. Dallinger, and 

 described in "The Microscope Figure 364. 



and its Revelations." A ver>- ,^^^,i„g ^^^^^ ^^-^^^ ^^ 

 good arrangement I have used conjugation, 



and which possesses the 



advantage of allowing several objectives on a 

 revolving nosepiece to be used rapidl\-, is the 

 following. A piece of thin cardboard has a circular 

 hole cut out of it, and the card is then cut to a 

 slightly smaller size than the ordinary three-inch by 

 one-inch slide. This pre()ared card is then soaked 

 in watir. the excess of water removed, and the card 

 lilat'cd upon a glass slide. Two cover glasses are 

 used, one slightly larger than the hole in the card, 

 the other being quite small, sa\' three-tenths of an 

 inch in diameter. The drop 

 of fluid to be examined is 

 [)laced between these cover 

 glasses and they are then placed 

 on the card, the smaller cover 

 glass being undermost : if a 

 small vessel of water is now- 

 placed in connection with the 

 card by means of filter paper 

 the preparation may be kept for 

 weeks w ithout evaporation from 

 the fluid under examination. It Conjugation. 



is almost impossible to get 



good permanent dried preparations of the monads, 

 as if dried im a cover-glass, like bacteria, they 

 break up, and the same result occurs if tixing 

 agents are used ; hence it is extremely difficult to 

 photograph the organisms, and recourse must be 



Figure 365. 



