ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
185 
Rotatoria. 
Constancy of Nuclei in Hydatina senta. — H. J. Van Cleave 
(. Proc . Amer. Soc. Zool. , 1922, 23 , 102). In 1912 Martini maintained 
that each individual of Hydatina senta has a fixed total of 959 nuclei. 
In 245 vitellaria Shull found (1918) 4 p.c. which did not show the 
customary eight nuclei, and some other discrepancies were observed. 
The author examined 435 gastric glands without discovering a single 
departure from the customary six nuclei. In 770 vitellaria only three* 
were found with supernumerary nuclei, two with ten, and one with 
twelve, instead of the normal eight. It may be said that there is 
almost absolute constancy in the nuclear numbers in this form. 
Experimental Study of a Rotifer. — Bessie Noyes (« Journ . Exper. 
Zool., 1922, 35 , 225-55). An account of normal life-cycle of Proales 
decipiens and of the results of experiments. The animal lives about a 
week, and then dies with characteristic symptoms of senility. During 
its life it produces several eggs per day, the number increasing to a 
maximum, then decreasing with the onset of old age. Reproduction 
by parthenogenesis for about 250 generations gave no indication of 
reduction of vigour in the race in any respect. During this period no 
males appeared. Environmental changes of various kinds failed to 
evoke males. So far as is known, the species may be quite without 
males. An attempt to increase the egg deposit and average length of 
life through artificial selection carried on for three months, in 15 
generations, was without avail, placing this organism in the list with 
other parthenogenetic forms in which selection is ineffective. Treat- 
ment with ethyl alcohol in a concentration of \ and J p.c. for twenty 
| weeks reduced the number of eggs produced from an average of 15 to 
24 in normal malted milk to an average of 10 to 14 in -J p.c. alcohol, 
and 3 to 5 in J p.c. alcohol, although the length of life was little 
influenced. The reduction in egg deposit brought about by alcohol 
was not retained beyond the third generation of descendants restored to 
| normal conditions of culture. J. A. T. 
Echinoderma. 
\ 
Amoebocytes of Holothurians. — Hjalmar Theel (. Arhiv . /. Zool. 
1921, 13 , No. 25, 1-40, 7 pis., 7 figs.). A study of hyaline plasma- 
i amoebocytes, bladder amoebocytes, spherule-containing amoebocytes, and 
crystal-containing amoebocytes in species of Gucumaria, Thy one, Psolus , 
Stichopus, and other genera. The bladder-cells seem to have escaped 
previous investigators. The bladders do not change their position 
within the cell ; they may be bent on themselves and lie in three planes. 
The crystals or spicules are formed as vital products within the amoe- 
bocytes. The skeleton of Echinoderms is due to the migration and 
syncytial fusion of calciferous amoebocytes. Different cells form different 
spicules in the same animal and apparently in the same conditions. 
J. A. T. 
