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Titre : Philosophical transactions of the Royal society of London. Series B, Biological sciences
Titre : Philosophical transactions of the Royal society of London. B
Auteur : Royal society (GB)
Éditeur : printed by Harrison and sons (London)
Éditeur : The Royal society (London)
Date d'édition : 1888-1990
Type : texte,publication en série imprimée
Langue : Anglais
Format : application/pdf
Identifiant : ark:/12148/cb34422226r/date
Identifiant : ISSN 00804622
Source : Bibliothèque nationale de France
Relation : http://catalogue.bnf.fr/ark:/12148/cb34422226r
Description : Variante(s) de titre : Philosophical transactions of the Royal society of London
Description : Variante(s) de titre : Philosophical transactions of the Royal society of London
Description : Périodicité : Irrégulier
Description : Etat de collection : 1888 (vol. 178)-1939
Provenance : bnf.fr
Date de mise en ligne : 13/01/2009
1908 (VOL199).
Page
(Screen 257 / 473)
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7 Q
VOL. OXCIX. – B. 2 G
DEVELOPMENT OF LARVAL NEPHRIDIA. 225
If not fed. after the third dav thev gradually dimmish in siz»
ordinary sea-water. If not fed, after thé third day they gradually dimfoish in siz»
and- finally break up at the'end of a few weeks, having made no further progress in
devèlopment. .S~M~SS~
As the adult worms are by po means very abundant at Naples, and thé number of
eggs obtained from a single worm is never very great, I experienced considérable
difliculty in obtaining sufficiènt material. On this account I adopted the môst
economical method of studying the material I obtained. 1 found the combiiled
celloidin-parafhn method of sectioning very useful, as by the use of this raethod very
little material is lost in the process ot embedding, and it is possible to section the
minutest larvée one at a time if necessary. It also has this advantage, that very
small sections can be traced in a rapid manner consecutively on the slide, by means
of the celloidin. On this account 1 did not adopt thé usual plan of dissolvïng it out,
but allowed it to remain on the slide as a means of readily finding the sections.
Material was fixed either in Flemming's strong solution, or Hermann's. For staining,
hasmacalcium and otlier hsematoxylin mixtures are most useful. For larvée to be
studied whole, dilute paracarmine, followed by slightly acid alcohol, gives very
satisfactory results.,
While the larva of Polygordius is found in thé tow abundantly during onlythe
months of February, March, and April, it is possible to rear the larva from the egg
throughout ail the spring and summer months. After the middle of September I had
some difticulty in obtaining the adults, so I have been unable to détermine whether
the sexual products are developed all the year round. The normal discharge of thèse
products seems to be restricted to the spring and, possibly, the summer months.
The free-swimming larvœ are found only during the spring and summer months
along the eastern coast of North America and. in the North Sea, while in the
Mediterranean they are found in February, March, and April, as already mentioned.
During the month of May, 1900, 1 obtained a number of Polygordius larvae from the
"tow" at Woods Holl, Massachusetts, which 1 had the opportunity of comparing
with the larvae found at*Naples; from these they can hardly be distinguished, and in
all essential featm-es, as I have already mentioned, they are the same.
I have considered it best in the foregoing work not to mention the various stages
by age, as development is affected by température to such an extent that there
is some uncertainty in designating stages by this^fuean's. The' progress made in
development in warm weather is twice as great as in the cold months of the early
spring. It is possible that under natural conditions developmeut may be still more
rapid for this reason time is a somewhat incertain manner of designating them.
Cowlks(3) states that he found the larva of P. appendieulatus go through metamor-
phosis in the course of a night under favourable conditions. He says, It surprised
me tofind that fully-developed swimming larvée, takén at night; and measuring slightly
less than 1 millim. in length, had metàmorphosed by the ilext morning. They were
at this time 2 millims. in length, showing an increase of 1 millim. in length (p. 125).
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