ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
49 
the fertilized eggs. Seven hundred and ninety-six females were, from 
their birth, kept isolated from males ; none of these produced any but 
the so called summer egg. One hundred and seventy-two females, 
opportunely placed with males, gave rise in eighty-four cases to fecun- 
dated eggs ; the other eighty-eight produced female parthenogeuetic 
eggs. All the copulations, therefore, were not fertilizing. The author 
thinks that, with a little more care, he might have obtained a larger 
number of fertilized eggs. The females should be fertilized six to 
eight hours after emergence ; some have been fertilized immediately on 
leaving the egg. Copulation may happen frequently after eggs have 
been deposited, but no further fertilization of eggs occurs. The males 
are polygamous, or may be so. In a further communication * M. 
Maupas states that he has discovered that copulation has no effect on 
those specimens that are about to lay female eggs. Each egg seems to 
be predestined to form a male or a female at the time when it is 
differentiated and begins to grow in the maternal ovary. The author 
does not despair of finding the time and causes which determine this. 
In Hydatina , as in some Hymenoptera, there is established between 
arrhenotoky (parthenogenetic production of males) and fecundating 
karyogamy, a relation so necessary that the second is impossible with- 
out the first. It is very proba'ble that this absolute connection between 
these two processes is commoner than we think, and that fresh researches 
will discover it in other parthenogenetic creatures. It was found by 
experiment that there is no advantage in cross-fertilization. 
Distribution of Pedalion mirum.| — Dr. O. E. Imhof draws atten- 
tion to various localities — Budapest, Galicia, Azores, North Italy, 
Germany, and others — in which this remarkable Rotifer has, in recent 
years, been found. The localities indicate that the creature lives in 
very varying conditions of existence. 
New American Rotifer .J — Dr. D. S. Kellicott describes a new 
species of the genus Cephalosiphon, which he calls C. furcillatus ; the 
dorsal antenna is provided with two stout, down-curved claws, the use of 
which is not quite clear. The entire length of the animal is 1/120 in. 
Echinodermata. 
Enteroccelic Nervous System of Echinoderms.§ — M. L. Cuenot 
describes a third system of nerves in Echinoderms. In the Asteroidea 
there is, on the aboral side of each arm, a strong muscular cord, which 
gives off branches in all directions, and functions chiefly as the antago- 
nist of the muscles which unite the ambulacral pieces. When a section 
is made of the wall of the body in this region, it is seen that the 
muscular bands are completely on the internal face of this wall. They 
are invested by a rather thick layer (40 p in Asterias glacialis), which is 
formed by a nerve-centre and the peritoneal epithelium. The nervous 
part is formed by fibrils, which take the same direction as the muscles, 
and inclose a rather large number of nerve-cells. The cells of the 
* T. c., pp. 505-7. 
t Zool. Anzeig., xiii. (1891) pp. 609-11. 
% Proc. Amer. Soc. Microscopists, xi. (1890) pp. 32-3 (1 fig.). 
§ Comptes Rendus, cxi. (1890) pp. 836-9. 
1891. 
E 
