ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
717 
nucleus has little or even no chromatin. In the motor nerve-cells of 
Mammals the chromatin is richly distributed in the cell-substance. 
There is generally a nucleolus, but this is rare in the cells of the 
neuroglia whose nuclei have many chromatin-granules. In motor nerve- 
cells the nucleolus is always excentric in position — a morphological fact 
perhaps of physiological interest. 
Bioplasts or Plastidules.* * * § — Drs. L. and R. Zoja have studied in 
various kinds of cells the bioplasts of Altmann or the plastidules of 
Maggi. Euchsinophilous elements or plastidules are widely diffused in 
all the animals, investigated. Their varied distribution in the cell is 
described, and particular attention is directed to their occurrence in 
spermatoblasts and spermatozoa. As to the probable function of the 
plastidules, the authors believe that they are nutritive. 
y. General. 
Nature and Origin of Variations.! — Prof. C. Lloyd Morgan took 
the nature and origin of variations as the subject of an interesting and 
philosophical address to the Bristol Naturalists. 
Exploration of Lakes. J — Dr. O. E. Imhof reports on recent progress 
in lacustrine zoology. The littoral fauna — from the shore to a depth 
of 20-25 metres — is richest. Zacharias has explored forty-two lakes, 
Seligo sixty-four, Ssowinsky seventy-five, and so on. The fauna of the 
deep water in Scandinavian lakes contains some forms identical with or 
closely related to marine forms in the North Sea and Baltic. Numerous 
Alpine lakes — there are 590 in the Canton of Graubiinden — have been 
searched. Almost all are rich in animal life, which persists even under 
cover of ice. Trout were found in Lej Sgrischus which lies 2640 
metres above the sea-level. Most is known about the surface animals. 
Of these many have a very wide distribution ; a few are quite local 
in their occurrence ; some are restricted to distinct limits of vertical 
distribution. The list includes about 27 species of Protozoa, about 
16 Rotifers, about 27 Copepods, about 46 Cladocera. As to number of 
individuals, one sample contained about 66,000 forms in a cubic metre, 
another about 113,040 ; but the number varies considerably at different 
periods. 
B. INVERTEBRATA. 
Animal Chlorophyll.§ — Prof. E. Ray Lankester calls attention to 
Dr. G. Haberlandt’s researches on the structure and significance of the 
chlorophyll-cells of Convoluta Boscoffensis. They have led to the sug- 
gestion that, whilst phylogenetically the cells must be regarded as Algae, 
yet at the present time they have by profound adaptation to life in and 
with the Convoluta , altogether lost their character as independent algal 
organisms, have become an integral histological element of the worm, 
and. in fact, constitute its assimilation tissue. Prof. Lankester points 
out that this hypothesis is in complete accord with the views several 
* Mem. R. 1st. Lomb. Sci., xvi. (1891) pp. 237-70 (2 pis.). 
f Proc. Bristol Natural. Soc., vi. (1891) pp. 249-73. 
X Ver. Schweiz. Naturf. Gesell., 1890 (pub 1891) pp. 157-70. 
§ Nature, xliv. (1891) pp. 465-6. 
