NO. 16. PROTOZOA ON THE ICEFLOES OF THE NORTH POLAR SEA. 11 



The dark specimens. I mentioned above that among the diatoms in 

 some ponds on the ice, I sometimes found numerous individuals actively 

 moving about; they had externally exactly the same shape and appearance 

 as the above transparent forms, and behaved in the same manner, but they 

 had a dark green, or almost black colour (see PI. II, Fig. 5). I do not think 

 that this was a different species, but rather believe that the dark colour might 

 be due to the food which the animals had eaten; and the stain might pro- 

 bably be contained in the oily globules. For the colour was evidently due 

 to dark grains or globules dispersed in the otherwise colourless protoplasm 

 (see PL II, Fig. 5). Unfortunately I did not get an opportunity of examining 

 whether these dark grains or globules were dissolved by transferring the spe- 

 cimens to Canada Balsam 1 . 



When individuals of this infusorium, either of the transparent form (Figs. 

 1 and 3) or of the dark form just mentioned, were followed under the micro- 

 scope for some hours, they were generally seen at last to contract into sphe- 

 roidal almost motionless globes shown in PL I, Figs. 10—12, and PL II, 

 Figs. 5—7. Figs. 10 (PL I) represents a colourless individual which was fol- 

 lowed from the very beginning, when it had the normal shape, like Figs. 5 

 and 3, and moved actively about, until it had contracted as represented, and 

 remained nearly motionless. The proboscis was now much reduced, and 

 merely formed a short protuberance. In the posterior region three vacuoles 

 were seen. (The figure is drawn with comparatively small magnification.) 



On July 28, 1894, I followed the formation of the quiescent globular 

 form of several dark individuals. The process was quite the same as observed 

 on transparent, and colourless individuals. I have given the following descrip- 

 tion of it in my note-book: 



1 In my note-book, July 2i, 1894, I find the following remarks aboufthese dark speci- 

 mens : "Individuals of exactly the same shape, appearance, and size as Figs. 6 & 7, 

 but perfectly dark or almost black, are seen in great number in the samples of dia- 

 toms from this ice -floe. Whilst the transparent form, Fig, 7, is, as a rule, colourless, 

 some individuals from this floe were greenish brown, I presume owing to chlorophyll 

 obtained from digested algae. I also presume that the dark colour mentioned above, 

 may be due to particles of food. The dark stain seemed to Joccur in the form of 

 lumps or globules, situated very near each other but still with transparent intervals 

 between them (cf. PI. II, Figs. 5 and 6). On one of these dark specimens I saw a dark 

 sausage-shaped body being pushed out of the posterior pointed end, the animal was 

 then in rapid motion. This dark body adhered for some time to what I consider to 

 be the anal opening, but soon dropped away. The oral opening I have not been able 

 to ascertain". 



