﻿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 distinction (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 not 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 gewohnlich drei Extremi- 

 tatenpaare auf, doch verlassen einige in hoherer Au.sbildung das Ei; so besitzen die jungen Pallenen') 

 beim Ausschliipfen bereits sammtliche Extremitaten und auch einige Arten der Gattung N\-mphon 

 erreichen schon im Ei diese hohere Entwickelungsstufe. Die verschiedenen Arten der letztgenannten 

 Gattung differiren iibrigens in dieser Beziehung, da die Larven einiger beim Ausschliipfen nur \-ier 

 Oder fiinf Extremitjitenpaare 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 etudes sur les 

 Pycnogonides» (1881), p. 482 seq. 



But before I pass to my own representation of the dexelopmental 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: Kroyer, Dohrn, Hoek and Morgan. 



Kroyer is the author to be named first, not only because he first of all has studied and de- 

 scribed larviE 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 pi. 39 of the great, unfinished 

 French work of travel: <Gaimard, Voyages en Scandinavie etc. (1849) ^^ which never appeared 

 any text or explanation. As such an explanation ma\' with regard to the Pycnogonida be taken 

 Kroyer's Contributions to our knowledge of the Pycnogonida*, <'Bidrag til Kundskab om Pycnogo- 

 niderne eller Sospindlerne > (1845). ^" the close of the third section of this treatise, on the metamor- 

 phoses of the Pycnogonida, I.e. p. 136 seq. Kroyer 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 Kjaeber (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 



') This statement doe.s not apply to all /V7//f«£-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 ambulator}- legs have been developed and before the 

 arising of the fourth pair and the ovigerous legs. 



