NovEMBER 27, 1913] 
not indigenous, and by encouraging the natives to keep 
domestic fowls round their villages, for such birds, 
when scratching up the ground, would find and 
destroy the pupze of Glossina; and (2) in areas where 
G. morsitans is common, by tarring or stopping up 
in some way all holes in trees near the villages. 
Bionomics of Amphidinium operculatum. 
Mr. R. Douglas Laurie described observations, 
made chiefly on the Cheshire coast, on this Peridinian, 
which occurs in such numbers as to form brownish- 
green patches on the sand, just below high-water 
mark of spring tides. The organism exhibits three 
eriodicities. (1) A daily periodicity; during the latter 
alf of February the patches were very evident on 
the surface of the sand until 10 a.m., then the 
organisms retired below the surface, reappearing 
shortly after noon, and reaching a maximum from 
2 to 4 p.m., after which they again disappeared. Ex- 
periments indicate that light and tide are the deter- 
mining factors, temperature being apparently unim- 
portant. (2) A lunar periodicity, “spring’’ periods of 
activity, alternating with “‘neap”’ periods of inactivity, 
being correlated with the amount of water in the 
sand, for the neap tides do not reach the region 
inhabited by Amphidinium. (3) An annual periodicity, 
a strongly marked maximum from February to the 
end of April being followed by decrease during May 
and June. The patches have not been seen on the 
sand since the first week of July, though microscopic 
examination showed that a few Amphidinium were 
still present. Mr. Laurie described a large and more 
elongate form of Amphidinium, which he is inclined 
to regard as a distinct species. 
Influence of Osmotic pressure on the Regeneration 
of Gunda. 
Miss Jordan Lloyd described observations on the 
small marine triclad Turbellarian, Gunda ulvae, which 
lives in great numbers at Plymouth, between tide- 
marks, and near the course of a small stream. The 
specimens employed in the experiments were about 
55 mm. long, and were cut transversely into two 
equal parts. The regeneration of the posterior region 
only was considered. Whole worms can live in water 
having an osmotic pressure between 2 and 33 atmo- 
spheres. Regulation of an anterior portion of Gunda, 
resulting in the production of a complete worm, takes 
fifty days in water having an osmotic pressure be- 
tween 15 and 22:5 atmospheres (the latter being that 
of ordinary sea-water). Lowering the osmotic pres- 
sure below 15 atmospheres retards the rate of regula- 
tion proportionately, and below 5 atmospheres no 
regulation occurs. Raising the osmotic pressure 
above 22-5 atmospheres retards the rate of regulation, 
and above 30 atmospheres no regulation occurs. The 
new posterior region is formed by the migration of 
large numbers of parenchyma-cells to the region of 
the wound, where they aggregate and build up the 
hew organs. Inhibition of regulation seems to be due 
to some factor which checks the migration of the 
parenchyma-cells. In examples showing retarded 
regulation, irregularities in the mitotic divisions of 
the parenchyma-cells have been noticed. 
Habits and Building Organ of the Tubicolous Poly- 
chaete, Pectinaria koreni. 
As the result of his observations on living Pectinaria, 
Mr. Arnold T. Watson considers that the process of 
tube-building is as follows :—A working space is first 
cleared, the sand around the lower, wider end of the 
tube, which is well below the surface, being removed 
by a very strong upward current, created within the 
tube by peristaltic action of the body-wall of the 
NO. 2300, VOL. 92]| 
NATURE 
385 
worm. This current causes the sand to pass rapidly 
through the tube, between it and the dorsal body- 
wall of the worm, and to be ejected through the small 
upper end of the tube, forming a mound on the sur- 
face of the sea-floor. A supply of sand is then carried 
by the tentacles to the head of the worm; one portion 
of this sand is swallowed for food and passes through 
the body of the worm, a second portion is carried 
by papilla, which form a track from the ventral edge 
of the peristomium to the bilobate building organ just 
below, on reaching which, each grain accepted for 
building purposes is received and held between the 
two lobes. These lobes apply the sand-grain to the 
free edge of the tube, where it is fixed by the cement 
poured out by the underlying cement-gland. 
Eelworms. 
Mr. Gilbert E. Johnson described some of the more 
recent work on eelworms (Anguillulide), a group of 
microscopic round-worms which, besides purely free- 
living forms, includes species living saprozoically in 
decaying substances, while others are parasitic in 
animals and plants. The saprozoic forms (Rhabditis, 
&c.) find their nourishment and multiply rapidly 
among the swarms of bacteria flourishing in sub- 
stances decaying in the soil and elsewhere, though 
whether the worms feed on the bacteria or on the 
products of their action is not yet known. The few 
species inhabiting animals, and regarded as parasites, 
are well exemplified by Rhabditis pellio, the larve 
of which inhabit the ccelom and nephridia of the 
earthworm. Mr. Johnson traced the life-history of 
this species, showing that the active forms in the 
nephridia, and the encysted forms in the coelom, re- 
main larval until the earthworm-host dies and decays 
in the soil. Then the eelworms feed in its decaying 
carcase, grow rapidly, become mature, and reproduce. 
When the nourishment from the dead earthworm is 
exhausted, the larvae wander into the soil and infect 
another worm, entering by the nephridiopores into the 
nephridia, and by the dorsal pores into the coelom. 
The larve entering the coelom are attacked as foreign 
bodies by the amcebocytes, and encyst. It is doubtful 
whether the term parasite should be used for this 
species, since the mode of nourishment is saprozoic. 
Other well-known eelworms—Tylenchus, Aphelenchus, 
and Heterodera—pierce the cellular tissue of plants 
by means of the hollow stylet protrusible from the 
mouth-cavity, and absorb the cell-sap. There are also 
numerous ‘semiparasitic'? forms, which occur round 
the roots of ordinary healthy plants, and apparently 
do no damage, but it would be interesting to ascertain 
what would be the result of their absence on the 
health of the plant. 
The Larva of the Star-fih, Porania pulvillus. 
Dr. J. F. Gemmill has traced the development of 
this star-fish. The eggs are small, and the general 
larval history is, similar to that of Asterias rubens. 
The late larva is a brachiolaria with a well-marked 
sucker, and numerous small papilla on and between 
the brachia. The features of special interest presented 
by the larvae were :—(1) The presence, in early larve, 
of possible rudiments of a posterior enterocoelic out- 
growth; (2) the occurrence, among the later larvee, of 
several specimens with double hydroccele formation ; 
and (3) the presence, in normal and in double-hydro- 
coele larva, of a ‘‘madreporic”’ vesicle, the floor of 
which contracted rhythmically during life. 
Observations on Artemia salina. 
Mr. T. J. Evans recorded observations made on 
this Crustacean, in graded strengths of sea-salt solu- 
tion from 4 to 25 per cent. It was found that, the 
