— At 
det voxne Dyr med udstrakt Fod, Tentakler og Sipho. Ungen 
adskiller sig nu fra det voxne Dyr kun derved, at de rota- 
toriske Organer ikke ganske ere forsvundne, at Conchylien 
endnu ikke er bleven haard, og at den blot har 1—2 Ven- 
dinger. Omtrent den 9de eller 10de Uge forlade Ungerne 
Kapslerne; de rotatoriske Organer ere nu aldeles forsvundne 
og man iagttager bag Tentaklerne en ophåiet Linie, som 
angiver det Sted, hvor de have siddet. 
Conchylien er bleven længere og nærmer sig i Formen 
det voxne Dyrs; den er haard, spröd og næsten ugjennem- 
sigtig, dog ere de sidste Vendinger endnu ikke udviklede. 
Vi have ikke omtalt den Maade, paa hvilken Organerne frem- 
staae; thi den afviger ikke i nogen Henseende fra Dannelsen 
hos Buccinum undatum. Men förend vi slutte denne vor 
Afhandling over Pectinibranchiernes Udviklingshistorie, finde 
vi det nådvendigt noget nærmere at omtale Dr. Carpenters 
Afhandling over Purpura lapillus, da de Resultater, han er 
kommen til, ere meget forskjellige fra vore. 
Vi ville her fremföre Hovedresultaterne med Forfatterens 
egne Ord. „The general result of my observations is, that 
the process has been altogether misconceived by my prede- 
cessors; that no such departure from the ordinary plan of 
development takes place, as the fusion of a number of ori- 
ginally distinct ova into a single embryo; but that each 
embryo originates in a single ovum; that it attains to a 
certain grade of development by the metamorphosis of the 
contents of its own vitellus; but that its increase in size, 
and the continuance of its development, depend upon its 
appropriation, by a process of deglutition or swallowing, of 
a mass of additional or supplementary vitellus, the want or 
insufficieney of which occasions its partial or complete 
abortion. As to the immediate cause of the production of 
„monstrous* embryos, therefore, — a phenomenon which I 
have found to be far more common than MM. Koren and 
Danielssen supposed, — I am in accordance with my pre- 
decessors, as I attribute it, with them, to the deficiency of 
nutritive material. But I differ from them essentially, not 
merely in regard to the mode in which this nutritive mate- 
rial is appropriated; but also in asserting that the production 
of embryos from single ova, instead of being an abnormal 
and occasional phenomenon, is one stage in the normal 
process of development.“ Med Hensyn til Antallet og Stör- 
relsen af de „egg-like bodies”, som Forfatteren benævner de 
i Kapslerne indesluttede Æg, da stemme de overeens med 
yore Undersögelser. Derimod har han ikke kunnet see 
Skalhuden, der dog for os har veret tydelig nok, og 
stundom veret tilstede efter at Furingen var indtraadt. Han 
har ikke seet nogen Kiimblere eller Kiimplet i disse „egg-like 
bodies“, men naar han tog Æg ud af Hggestokken, som vare 
ner Modenhed, saa fandt han, at disse havde samme Stör- 
relse, som denevynte „egg-like bodies“ og vare forsynede med 
Kiimblere og Kiimplet. Heri stemme vi fuldkommen overcens. 
Carpenter siger imidlertid, at han i enhver Kapsel har 
fundet, foruden de ,egg-like bodies,“ en Deel virkelige Æg; 


capsules, et quand dans ce stade on en ote un, il se met 
a ramper comme l’animal adulte, le pied, les tentacules et 
le siphon étendus. Il se distingue alors de l’adulte en ce, 
que les roues n’ont pas encore disparu complétement, que la 
coquille n’est pas encore dure, etfaussi par la spire qui n’a 
qu’un, ou au plus, deux tours. A partir de la neuviéme ou 
dixieme semaine les jeunes abandonnent les capsules; les 
roues ont alors disparu, et l’on observe derriére les tenta- 
cules une ligne élevée qui indique le lieu qu’ils ont occupé. 
La coquille est devenue plus alongée, et se rapproche 
plus de celle de l’adulte; elle est dure, cassante et presque 
opaque; cependant les derniers tours de spire ne sont pas 
encore developpes. Nous n’avons pas parlé de la maniere 
dont le développement des organes se fait, parcequ’elle ne 
differe pas de celle qui a lieu chez le Buccinum undatum, 
Mais avant que nous terminions notre traite sur l’histoire du 
développement des Pectinibranches, nous trouvons qwil est 
nécessaire de reprendre le traité de Ms le Dr. Carpenter 
sur la Purpura lapillus, puisque les résultats quil a obtenus, 
sont trés différents des nåtres. 
Nous allons en exposer les traits les plus remarquables 
par les propres paroles de l’auteur: — „The general result 
of my observations is, that the process has been altogether 
misconceived by my predecessors; that no such departure 
from the ordinary plan of development takes place, as the 
fusion of a number of originally distinct ova into a single 
embryo; but that each embryo originates in a single ovum; 
that it attains to a certain grade of development by the me- 
tamorphosis of the contents of its own vitellus; but that its 
increase in size, and the continuance of its development, de- 
pend upon its appropriation by a process of deglutition or 
swallowing, of a mass of additional or supplementary vitel- 
lus, the want or insufficiency of which occasions its partial 
or complete abortion. As to the immediate cause of the 
production of ,monstrous* embryos, therefore, — a phenome- 
non which I have found to be far more common than Mm. 
Koren and Danielssen supposed, — I am in accordance with 
my predecessors, as I attribute it, with them, to the difici- 
eney of nutritive material. But I differ from them essenti- 
ally, not merely in regard to the mode in which this nutri- 
tive material is appropriated; but also in asserting that the 
production of embryos from single ova, instead of being an 
abnormal and occasional phenomenon, is one stage in the 
normal process of development.” — Le nombre et le volume 
des „egg-like bodies,” qui est le nom, que l’auteur donne 
aux aufs renfermés dans les capsules, s’accordent avec nos 
observations sur ces ceufs. Mais il n’a pas pu découvrir le 
chorion, qui pourtant nous a paru trés distinct, et qui quel- 
ques fois méme s’est laissé voir apres l’avenue du sillonne- 
ment. Il n’a remarqué ni une vésicule germinative ni une 
tache germinative chez ces „egg-like bodies ;* mais en sortant 
de l’ovaire des ceufs a peu-prés développés, il trouva que 
ceux-ci étaient du méme volume que les „egg-like bodies“ et 
étaient munis d’une vésicule germinalive et d'une tache ger- 
minative. Nous nous accordons parfaitement en cela. 
Cependant Mr Carpenter dit, qu'il a trouvé dans chaque 
capsule, sans compter les „egg-like bodies,” de véritables æufs. 
6 
