12 PYCNOGONIDA. 
is made between the embryonal and the larval stage, cannot be fully kept up with regard to the 
development of the Pycnogonida. The general mark of distinetion (whether the embryo has or has 
not left the egg) is here of only very little importance, and nearly related forms, even species of the 
same genus, may attain to a different, sometimes very different development in the egg. Accordingly 
it will not do to deny the metamorphosis in such forms as do mot leave the egg until they have 
attained their permanent shape. This opinion and the interpretation of the larval development now 
generally current have been expressed by Korschelt a. Heider (1890) p. 662 seq: «Die meisten 
Pantopoden entwickeln sich mittelst Metamorphose. Ihre Larven weisen gewéhnlich drei Extremi- 
tåtenpaare auf, doch verlassen einige in håherer Ausbildung das Ei; so besitzen die jungen Pallenen-") 
beim Ausschlipfen bereits såmmtliche Extremitåten und auch einige Arten der Gattung Nymphon 
erreichen schon im Ei diese håhere Entwickelungsstufe. Die verschiedenen Arten der letztgenannten 
Gattung differiren tubrigens in dieser Beziehung, da die Larven einiger beim Ausschlupfen nur vier 
oder funf Extremitåtenpaare aufweisen (Hoek).» As will be seen from this quotation, Korschelt and 
Heider found their statement especially on the examinations by Hoek, or recapitulate the principal 
contents of the description of Hoek as it is given in his last great work: «Nouvelles études sur les 
Pycnogonides» (1881), p. 482 seq. 
But before I pass to my own representation of the developmental history I shall give a short 
historical view of the most important works in this branch of study, and as we have already in 
Dohrn: «Die Pantopoden des Golfes von Neapel» (1881) a very copious literary survey, I may limit 
myself to the following four authors: Krøyer, Dohrn, Hoek and Morgan. 
Krøyer is the author to be named first, not only because he first of all has studied and de- 
scribed larvæ of the Pycnogonida, but also on account of his contributions being the most important 
ones we hitherto have got concerning the development of these animals. Already his «Om Pycnogo- 
nidernes Forvandlinger» («On the metamorphoses of the Pycnogonida») (1840) is of great importance, 
but still more so is the series of representations of larval forms given on pl. 39 of the great, unfinished 
French work of travel: «Gaimard, Voyages en Scandinavie» etc. (1849) to which never appeared 
any text or explanation. As such an explanation may with regard to the Pycnogonida be taken 
Krøyer's «Contributions to our knowledge of the Pycnogonida», «Bidrag til Kundskab om Pycnogo- 
niderne eller Søspindlerne» (1845). In the close of the third section of this treatise, on the metamor- 
phoses of the Pycnogonida, 1.c. p. 136 seq. Krøyer collects the laws that seem to regulate the devel- 
opment of the Pycnogonida under 5 principal heads which may briefly be rendered thus: 1? The 
Pycnogonida pass through 3 stages. 2? The first stage is of a thick, swollen shape; filled with yolk 
substance; without any abdomen; with a proboscis; with cheliferous «Kindbakker» (mandibles); 
and with 2 pairs of feet. Eyes seem to be wanting. 3? In the second stage a third pair of feet 
are found, but they are short, and have only an indistinct articulation, or none at all. Eyes as well as 
the first and second pair of «Kjæber» (maxilles) can be distinguished, at;least in some species. Some- 
times the yolk substance of the body is present, in which case the young one passes this stage under 
1) This statement does not apply to all Pa//ene-species. The species of this genus that I have examined, as will be 
shown in the following, leave the egg, when the three foremost pairs of ambulatory legs have been developed and before the 
arising of the fourth pair and the ovigerous legs. 
