ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
199 
examples of workmanship than the tube of Amphictione , or that of 
Terebella , with its terminal fringe. Even man, with all his ingenuity, 
has to make frames for constructing arches and circular buildings, and 
moulds for circular casts ; his cement has to be brought from a distance 
and carefully manufactured, and he requires good sight and much aid 
to form his dwelling; some of the most skilful and beautiful formations 
of these marine Annelids are executed by creatures devoid of eyes, and 
with a soft and delicate body, whose mortar is secreted by the glands 
of their skins, and whose inherent instinct enables them to dispense 
with all artificial aid in the construction of their homes. 
The Genus Polydora.* — Sig. D. Carazzi describes the Mediterranean 
species of Polydora Bose. (. Leucodore Johnston), and discusses briefly the 
other four known species. 
More interesting is his account of the way in which P. ciliata and 
P. hoplura attack oysters. The first does serious damage, the second 
much less. The second species is a true borer, making galleries in the 
oyster-shell. It may destroy the insertion of the adductor muscle, 
and thus kill the mollusc. The first species enters when the valves are 
gaping, and nestling near the mantle-edge accumulates patches of mud 
which have a disastrous effect. Whitelegge appears to have confused 
the two species. Neither can be called a parasite, they are rather 
commensals. 
Amcebocytes and Oogenesis in Micronereis variegata.f — M. E. G. 
Racovitza finds that the amcebocytes of this worm are not formed in the 
adult segments of the animal, but are derived directly from the un- 
differentiated mesodermic mass of a developing segment. This mass is 
an active centre of mitotic division, and in it there are to be found nuclei 
which are larger than the rest; these are the nuclei of the oospores. 
These last begin to divide very early and give rise to ten daughter-cells, 
each of which forms a small morula-like mass. The nuclei form and a 
homogeneous nucleolus appears ; one of the cells, the future egg, grows 
very rapidly. Its cytoplasm is charged with droplets of fat, which 
gradually disappear to make way for small spherical globules. The 
nucleus and nucleolus have, meantime, both increased in size. The 
other daughter-cells, the cytoplasm of which has not increased in volume, 
form a small mass at one of the poles cf ‘he egg, and finally disappear. 
The mature ovum has a delicate vitelline membrane surrounding a 
yolk which, in the first state, is formed of apparently homogeneous 
globules, all of the same size. The germinal vesicle, surrounded by a 
delicate membrane, has finely granular contents, and in the interior of 
the nucleolus there is a small spherical vesicle. As the eggs are very 
large (240 /*) in relation to the size of the animal (350 /x wide), and as 
there are no segmental organs, the evacuation of the ova must be effected 
in a special way ; they would appear to pass out by an orifice placed 
superiorly to the anus. 
A Polynoid with Branchise.f — Under the name of Eupolyodontes 
Cornishi Miss F. Buchanan describes a new Polychaete taken off the 
* MT. Zool. Stat. Neapel, xi. (1893) pp. 4-45 (1 pi.). 
t Comptes Rendus, cxviii. (1894) pp. 153-5. 
X Quart. Journ. Micr. Sci., xxxv. (1893) pp. 433-50 (1 pi.). 
