i i re ll ee 
ia. 
Aiggets Blommemasse ikke undergaar nogen Kloy- 
ning. Ifolge Kowalewsky dannes det blastodermale 
Cellelag ved den successive Klovning af en enkelt 
stor Polarcelle. Paa et temmelig tidligt Udviklings- 
stadium, som er fremstillet Pl. V, Fig. 6, finder vi, 
at Blommemassen i den ene Halvdel af Agget er 
begerformigt omgivet af et Lag af klare Cellier, der 
naynlig i Kanten af Agget tydeligt hever sig af 
fra den mere ugjennemsigtige redgule Blommemasse. 
Dette er den sig dannende Blastoderm. Det forste 
Anleg til Embryonet antydes ved en svag trans 
versal Indbugtning i Blastodermen, begreendset af 
2 noget fremspringende Vulster. Den ene af disse 
Vulster forestiller Overleben, den anden Haleenden 
(se Fig. 7 og 8). Til, hver Side af den ovenomtalte 
Indbugtning viser sig noget senere 3 tverstillede 
langagtige Forhoininger, der forestiller Anlegget 
til de 2 Par Folere og Mandibularpalperne, og foran 
dem sees til hver Side en utydeligt begrendset 
rundagtig Udvidning, der aabenbart er Anlegget til 
Oienstilkene. Embryonet, der endnu er omgivet af 
ggehinden, befinder sig nu i det saakaldte Nauplius- 
stadium. Senere optreder, bag de 3 Par ovenomtalte 
Lemmeanleg, successivt en dobbelt Rekke af min- 
dre Forhoininger, der antyder Anlegget til de fol- 
gende Lemmer (se Fig. 7). Samtidigt bliver den 
transversale Indbugtning dybere, Haleenden sondrer 
sig tydeligere og streber at fjerne sig fra Over- 
leben, hvad der tilsidst, i Forbindelse med Embry- 
onets Veext, har tilfolge at Aiggehinden brister og 
skaller af. Det Stadium, som nu folger, er det saa- 
kaldte Puppestadium, som er fremstillet Fig. 9 og 
10. Embryonet, som nu kun er omgivet af en over- 
ordentlig tynd og gjennemsigtig Membran, Larve- 
huden, viser ikke lengere den oprindelige ventrale 
Krumning, men har strakt sig fuldt ud i Lengden 
og endog antaget en svag dorsal Boining. Formen 
er nesten kolledannet, idet Legemet fortil ligesom 
er opblest, paa Grund af en betydelig Rest af 
Blommemassen, der fylder det her dorsalt. Man 
kan saaledes egentlig paa Legemet adskille to tem- 
melig skarpt sondrede Hoveddele, en nesten kugle- 
formigt opsvulmet forreste Del, og en betydelig 
smalere, nesten cylindrisk og bagtil i.en stump 
' Spids udgaaende Del. Den forste svarer nermest 
til Hovedet hos det voxne Dyr, medens den. sidste 
i sig indbefatter baade Midtkrop, Bagkrop og Hale. 
Saavel paa den forreste som bagerste Del kan der 
nu adskilles en dobbelt Rekke af lemmelignende 
Fremspring, men af et endnu yderst ufuldkomment 
Udseende, kun dannende. simple koniskt tillobende 
Fortsatser. Storst og tydeligst sondrede er de 2 
forreste Par (a', a*) som forestiller de 2 Par Folere. 
De har en nesten poelsedannet Form og er boiede 
bagud langs Siderne af Forkroppen. Imellem dem 
i Midten sees et tydeligt klapformigt Fremspring (L), 
som er Overleben, og foran dem til hver Side en 
27 
a somewhat lighter colour and also become more 
transparent. They are, as in most of the Crustacea, 
meroblastic, as the greater part of the ovum’s yolk 
does not undergo any segmentation. According to 
Kowalewsky, the blastodermatic cellular layer is 
formed by the successive segmentation of a single 
large polar cell. In a pretty early stage of devel- 
opment, which is represented in PI. 4, fig. 6, we find 
that the yolk in the one half of the ovum is sur- 
rounded by a cup-shaped layer of clear cells which, 
especially on the edge of the ovum, distinguish 
themselves from the more opaque red-yellow yolk. 
That is the Blastoderm in course of formation. The 
first rudiments of the embryo is indicated by a 
faint transversal incurvation of the blastoderm, 
limited by 2 projecting swellings. The one of these 
swellings represents the upper lip, the other the 
caudal extremity (see fig. 7 and 8). On each side 
of the above-mentioned in-curvature there, somewhat 
later, appear 3 transversally placed, elongate pro- 
minences which represent the rudiments of the 2 
pairs of antenne and the palpi of the mandibles; and 
in front of them there is seen on either side an 
indistinctly limited, roundish dilatation, which is evi- 
dently the rudiment of the ocular peduncles. The 
embryo, which is still surrounded by the skin of the 
ovum, finds itself now in the so-called Nauplius 
stage. Subsequently there appears, behind the rudi- 
ments of the 3 pairs of appendages above mentioned, 
successively, a double series of smaller prominences, 
which indicate the rudiments of the succeeding appen- 
dages (see fig. 7). At the same time the transversal 
in-curvature becomes deeper, the caudal extremity 
separates itself more distinctly and endeavours to 
remove itself from the upper lip, with the eventual 
effect, in connection with the growth of the embryon, 
that the skin of the ovum bursts and scales off. The 
stage which now succeeds is the so-called pupa stage, 
represented in fig. 9 and 10. The embryo, which is 
now only surrounded by an extraordinarily thin and 
transparent membrane, the larval skin, no longer 
exhibits the original ventral curvature, but has 
stretched ‘itself fully out in length, and even as- 
sumed a faint dorsal curvature. The shape is almost 
clavate, as the body in front is, as it were, blown 
out, owing to a considerable remnant of the yolk 
substance which here occupies it dorsally. We can 
thus in the body really distinguish two pretty 
sharply separated chief parts, an almost globularly 
shaped swollen front part, and a considerably .narr- 
ower, almost cylindrical, part passing out in a blunt 
point behind. The first named corresponds closest 
to the head of the adult animal, while the last- 
named contains within itself the mesosome, the 
metasome and the urosome. In the front, as well 
as in the posterior part, there can now be dis- 
tinguished a double series of limb-like prominences 
