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The first Paper of this Session, being the first read before 
the Section, was one by Mr. Go. Mostey, on 
“ Daphnia Pulex,’ March 21st, 1859. 
—_—_— 
Mr. Mostey commenced his account of the animal by 
enumerating some of its principal historians and describers 
from the year 1669 to the recent account of it by Baird, 
published in the Ray Society’s volume for 1850. After 
giving descriptions of the animal, as it appears under 50 
and 200 linear magnifying power, Mr. Mosley proceeded 
specially to examine a doubtful organ on the head of this 
crustacean. 
“ Proceeding,” he says, “from the upper frontal extre- 
mity, a nerve about 335 of an inch in length is produced 
to a small oval black spot soo of an inch in its long dia- 
meter, situated between the eye and the beak. Baird does 
not name this organ in the Daphnia. In the Microthrix 
it is so much developed that he marks it as characteristic : 
‘Eye accompanied with a black spot.’ This black spot was 
noticed by Miiller, who considered it to be another eye. 
Jurine differs from this opinion, though unable to dis- 
cover its real utility ; so does Strauss, who found it in the 
embryo before birth, exactly as in the adult. Baird agrees 
with these last authors, that it is not an organ of vision. 
Dr. Zenker, in the Microscopical Magazine for 1850, vol. ii. 
second series, says it has been looked upon as an auditory 
organ, but compares it with the tripartite azygos eye, 
which occurs extensively in the crustaceans ; but he leaves 
the question much as he found it. He says it is the first- 
deyeloped organ of sense, and, reasoning from analogy 
