168 ANNALS OF SCOTTISH NATURAL HISTORY 
prolific some of these creatures are, the following statements 
are submitted :—-A few months ago, when examining some 
gatherings of freshwater entomostraca, I selected at random 
ten specimens of Daphnza pulex and counted the number of 
ova and embryos in each: in some of the specimens the ova 
were in the earlier stages of development, in others the 
embryos were well formed. The first specimen examined 
contained 27 ova; in the second there were 30; in the 
third, 32; in the fourth, 20; in the fifth, 23 > im thessrcem 
32); in the seventh, 18 ; in the eighth, 18 ; in theimimtagnioe 
and in the tenth, 20—in all 236 ova and embryos, or an 
average of 23.6 for each Daphnia. Many years ago the late 
Dr. Baird, the eminent English naturalist, made a number of 
experiments with Daphnia pulex, and the following brief 
statement of some of the results he obtained throws much 
light on the fecundity of the species! I give the results of 
the experiments in his own words :—*“ 29th November, I 
isolated a D. pulex with an ephippium; 30th, ephippium 
is thrown off; 4th December, Daphnia has eggs; 8th, young 
ones are born; gth, the mother, having been removed from 
the young immediately after their birth, was found to have 
eggs again; 16th, young ones born; 20th, has eggs again ; 
24th, young ones born; 25th, has eggs again; 6th January, 
young born—mother has eggs in ovary again; 14th, young 
born—mother has eggs again; 22nd, young born; Ist 
February, has eggs again; 8th, young born. 
“On the 8th December, isolated one of the young born - 
from the subject of last series of observations on 30th 
November. On the 21st December she was found to have 
eggs; 28th, young born; 29th, has eggs again; gth January, 
young born—mother has eggs again; 24th, young born; 
25th, has eggs again; Ist February, young born—mother 
has eggs again; 9th, young born; 27th, has eggs again; 
8th March, young born” (“ Natural History of the British 
Entomostraca,” p. 80, 1850). Dr. Baird also states that he 
isolated two specimens born on 18th January, and that both 
1 Although Dr. Baird’s experiments are made use of here to prove the fertility 
of Daphnia, the purpose he had in view was rather to show that though the 
Daphniz are not hermaphrodite, as had been supposed, one union with the male 
*‘is sufficient not only to fecundate the mother for her life, but all her female 
descendants for several successive generations.” 
