178 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



number of constituent amcebse from 18a long by S/x broad to iSfj. long by 23// broad. 

 In fusing the amccbre adliere closely to one another, finally after some time fusing 

 into one mass, which can then undergo further movements. Nuclei (pi. 4, fig. 8 N) 

 of plasiiiode vesicular, 2 to 3 according to the number of constituent aincebiu. 

 Union or fusion of the nuclei not directly observed; regarded, however, as very 

 probable, as frequently pretty large plasinodes of 22// and 18// (doubtless 

 [Page 19] formed by fusion of 2 or 3 am<eb;c) were seen containing only 1 large, 

 vesicular nucleus (pi. 5, fig. 2 N). Besides, plasmodes seen to originate 

 by fusion of 3 amujbui and to contain nuclei, showed on the next day only 1 large 

 nucleus. 



Contractile vacuole not demonstrable with certainty in fusion plasmodes; its 

 presence, however, not regarded as impossible ; the plasma, on the contrary, con- 

 tains so many vacuoles as to appear vacuolate or frothy. Motion of plasmodes 

 ratlier slow. Plasma in the next 24 hours undergwing a change; the frothy, vacuo- 

 late structure changing to a finely granular condition, the vacmdes vanishing. 

 Nucleus, also, no longer visible; probably transformed by division iuto several 

 globular strongly relringent bodies (pi. 5, fig. 3 N), though this was not directly 

 observed. Motion of phismode in this stage quite slow, ceasing entirely after some 

 time; encystment following in 1 or 2 days. 



2. Encystment. — The encystment of simple small amrebro and the alterations in 

 their body jilasma is first described; afterward the process witli the fusion plas- 

 modes. With the small amoebaj encystment begins when they have attaine<l a certain 

 size. They gradually draw in their lobulate pseudopodia and acquire an irregular, 

 more or less oval or pyriform shape. Locomotion still takes place, thongh very 

 slowly, small ragged pseudopodia being still emitted. After about 1 hour this move- 

 ment also ceases and the amoeba revolves slowly, gradually rounding itself oft" and 

 assuming with a state of rest a nearly globular form. After about 10 hours it has 

 transformed itself into a proper cyst (pi. 4, fig. 3) about 10// in diameter, 

 [Pago 20] consisting of a plainly bordered, extremely thin membrane and finely 

 granular contents, in which individual, small, strongly refringent gran- 

 ules, a vesicular nucleus (N), and a contractile vacuole (c. v.), which now pulsates 

 markedly more slowly, are percey)tible. 



After about 24 hours (pi. 4, fig. 4) the membrane appears markedly thicker, double 

 contoured, and the strongly refringent granules have increased in number. The 

 nucleus no longer appears vesicular, but homogeneous and rather strongly refringent. 

 Contractile vacuole still always visible, although now pulsating extremely slowly 

 (about once in 5 minutes). 



After another 24 hours (pi. 4, fig. .5) the protoplasm appears strongly brilliant, the 

 contractile vacuole has vanished, and the nucleus is not perceptible. In their places 

 are observed several round, strongly refringent structures (probably proceeding 

 from division of the nucleus), dift'erentiated from the other cyst-plasma granules 

 already mentioned, by their more considerable size and their affinity for stains. 

 Though the falling to pieces of the nucleus was not directly observed, the granules 

 may with tolerable safety be admitted to hav(! originated through nuclear division. 

 Schewiakolf thinks that first the nucleus divides, and about 10 hours later the spores 

 (pi. 4, fig. 6) are formed, since around every nucleus a portion of the protoplasm 

 delimits itself from the remainder. 



Encystment of plasmodes occurs in the same w:iy. Locomotion becomes con- 

 tinually slower until finally it is extinguished. The plasmode then rounds itself 

 ofl", acquires a somewhat elongate oval form, which, as also the size, varies 

 greatly. It then secretes a thin membrane, which envelops it closely on every side 



(pi. .5, fig. 4). 

 [Page 21] In 1 to 2 days the membrane becomes markedly thicker, then appearing 

 homogeneous, strongly rcfringeut ?m4 doubje contoured, During the 

 nejtt day spore forpiation begins. 



