fra buede Sideribber udgaar til den modstaaende 
Udvidning, hvilken sidste ender med en tilskjerpet 
Kant og viser en fint cellulos Structur (se Fig. 23). 
Ved hvilke mekaniske Midler denne eiendommelige 
Form af Xgkapselen, der er noiagtig ligedan hos 
alle Ag, tilveiebringes, er ikke saa godt at sige. 
Rimeligvis spiller herved den skrueformige Dreining 
af Ovarialtuberne en vesentlig Rolle. AZgmassen 
bliver med visse Mellemrum, rimeligvis i Forbindelse 
med Hnudskiftningsakten, udstodt af Skallen, og fal- 
der derpaa tilbunds, hvor den indleires i Mudret. 
Imidlertid har Ovarierne produceret et nyt Set Mg, 
som snart samler sig til en ny Augmasse under den 
dorsale Del af Skallen. Paa denne Maade kan et 
og samme Individ i Lobet af nogle Uger producere 
et enormt Antal af Mg. Disse udklekkes dog i 
Regelen aldrig samme Aar, som de er lagte, men 
er alle bestemte til at overvintre; ja der er Grund 
til at antage, at de i mange Tilfelde kan henligge 
i en hvilende Tilstand gjennem meget lange Tids- 
rum, tildels fuldstendig indtorrede, for de ud- 
klekkes. 
Udvikling. — Om Udviklingen af denne Phyllo- 
pode har den franske Naturforsker Lereboullet i 
Aaret 18661) leveret en meget udforlig, af Afbild-. 
ninger ledsaget Fremstilling, hvortil senere Forskere 
altid har henholdt sig, uden at der, saavidt mig 
bekjendt, er anstillet fornyede Undersogelser over 
denne Side af nerverende Forms Biologi. Ogsaa 
Kjonsorganernes Bygning er af samme Forsker 
meget udforligt omtalt i samme Afhandling, men 
hans Fremstilling er her i flere vesentlige Punkter 
urigtig og misvisende. Da jeg har havt en sjelden 
god Anledning til at studere denne Forms Udvik- 
ling og tror i flere vesentlige Punkter at kunne 
supplere og berigtige den af Lereboullet givne Frem- 
stilling, skal jeg i det folgende forsoge noget ud- 
forligere at beskrive samme. 
Udviklingen kan passende inddeles i 2 Perioder, 
den larvale og postlarvale, begge vel markerede fra 
hinanden. Den forste Periode er tilendebragt i 
meget kort Tid, ialmindelighed i Lobet af nogle faa 
Dage, hvorimod der til den anden Periode udkreves 
mindst en hel Maaned. 
Larveudviklingen. — Larven kommer til Ver- 
den i en yderst ufuldkommen Tilstand, som en saa- 
kaldt Nauplius, uden at vise nogensomhelst Lighed 
med det voxne Dyr. Legemet har i dette Iste Sta- 
dium (Tab. XVII, Fig. 1) kun en Lengde af 0,25 
mm. og bestaar af 2 ved en svag median Indknib- 
ning sondrede Afsnit af omtrent lige Storrelse. Det 
forreste Afsnit repreesenterer Hovedet, det bagerste 
*) Annales des Sciences naturelles, Zoologie, 5me Série, T. V, 
100 
figs. 20, 21, 22) with 2 wing-like expansions placed 
perpendicular to one another. Along one of these 
expansions runs a distinctly thickened rib, from 
which curved lateral ribs run to the opposite expan- 
sion, this last ending in a sharp edge, and exhibiting 
a finely cellular structure (see fig. 23). By what 
mechanical means this peculiar form of egg-capsule, 
which is exactly similar in all the ova, is brought 
about, it is not easy to say. Probably the screw- 
like twist of the ovarial tubes has much to do with 
it. The egg-mass, at certain intervals, probably 
connected with the process of exuviation, is thrust 
out, of the shell, and thereupon sinks to the 
bottom, where it is imbedded in the mud. In the 
meantime the ovaries have produced a new set of 
ova, which soon collect into a new egg-mass beneath 
the dorsal part of the shell. In this way, one 
animal, in the course of a few weeks, can produce 
an enormous number of eggs. These, however, as a 
rule, are never hatched in the same year that they 
are laid, but are all designed to stand a winter; 
indeed, there is reason to suppose that in many 
cases they may lie in a state of quiescence for 
very long periods of time, sometimes completely 
dried up, before they are hatched. 
Development. — The French naturalist Lere- 
boullet, in the year 1866+), published a very detailed 
account of the development of this Phyllopod, 
accompanied by illustrations; and more recent na- 
turalists have always referred to this, without, as 
far as I am aware, any fresh investigations on this 
point in the biology of the present form having 
been instituted. The structure of the sexual organs 
is also very fully described in the above treatise, 
but here his description, in many essential points is 
incorrect and misleading. As I have had an unu- 
sually good opportunity of studying the develop- 
ment of this form, and believe that in several 
important points I can supplement and correct the 
account given by Lereboullet, I will here endeavour 
to describe it somewhat more fully. 
The development may be suitably divided into 
2 periods, the larval and the post-larval, both well- 
marked. The first period is brought to a conclusion 
in a very short time, generally in a few days, 
whereas at least a month is required for the second. . 
Larval Development. — The larva is brought 
into the world in an exceedingly imperfect condition, 
as a so-called nauplius, without exhibiting any 
resemblance whatever to the adult animal. The 
body in this 1st stage (Pl. XVII, fig. 1) has a length 
of only 0.25 mm., and consists of 2 sections of about 
equal size, defined by a slight median contraction. 
The front section represents the head, the hind one, the 
1) Annales des Sciences naturelles, Zoologie, 5me Série, T. V. 
