TJic If isk Naiufalist. August-September, 
in length and nearly an inch in breadth, while the ova 
amounted to about 50,000," and quote Bouchard Chantereux 
as having found a coil 12 inches long with 80,000 ova in 
what appears to be a variety of the same species. Sir 
Charles Eliot (Part viii., Aid. & Hancock Monograph) says 
the coil may be as much as 15 inches long when extended. 
Four coils taken by me at Bullock and Dalkey Island in 
April, 1914, when opened out carefully without stretching 
were found to have lengths of 32 inches, 28 inches, 26-| 
inches and 17 inches, respectively, with a breadth varying 
from f to inch. The number of ova in the longest of 
these ribbons was found to be fully 645,000, the calculation 
being made as follows. A piece of the ribbon exactly 
one-eighth of an inch square was cut out and subjected 
to gentle pressure between two glass slides so that the 
ova were well separated. Carefully counted, the ova in 
this piece were found to number 360. The total area of 
the ribbon was found to contain 1,792 pieces one-eighth inch 
square and, assuming the ova to be, as they appeared to 
be, quite evenly distributed in the ribbon, a simple multipli- 
cation gave the total as 645,120. 
Darwin (Voyage of the Beagle, chapter ix., footnote) has 
calculated at 600,000 the number of eggs in the ribbon 
nearly 20 inches long of a Falkland Island Doris and gives 
this as an instance of the fallacy that the numbers of a 
species depend on its powers of propagation. Our native 
D.tuherculata offers an equally good illustration of the fallacy; 
for it is no more abundant than the Falkland Island species 
and much less so than, for instance, Actaeonia Cocksi whose 
egg clusters contain usually but a dozen eggs. 
Jorunna Johnstoni (Aid. & Hanc.) 
Doris Johnstoni. 
Between tide-marks ; rare. " In July last Mr. Hynd- 
man procured a specimen of this Doris on Fuci at Skerries " 
Thompson '45 (sub. D. ohvelata). Three specimens, the 
largest over two inches (50 mm.) long, under a ock at low 
tide, Dalkey Island, June, 1908 : Colgan, '09. One speci- 
men at Shennick's Island, Skerries, July, 1910, and another 
