16 PYCNOGONIDA. 
development taking place before this act, is reckoned to the embryonal stage, but that I cannot agree 
with this view. As the embryo, however, in the different Pycnogonida, breaks the egg shell some- 
times after å shorter, sometimes after a longer development, nay, sometimes not even, until all the 
limbs, the ambulatory legs included, have been developed, it will be understood that Korschelt and 
Heider, Lehrb. Entwick. wirbell. Thier. 1890, in their large, well known text book can say of the 
Pycnogonida that only «die meisten Pantopoden entwickeln sich mittelst Metamorphose», 1. c. p. 662, 
as if there were any important difference between the different Pycnogonida; Dohrn, Pantop. Golf. 
Neap. 1881, even says l.c. p.77: «Pallene hat die ganze Larvenentwickelung vollkommen unter- 
druckt, das junge Thier, welches die Eischale verlåsst, besitzt bereits alle definitive Extremitåten, 
wenn auch noch nicht in definitiver Gestalt.» On the following page we find: «Wenn der Embryo 
seine Reife erreicht hat, gleicht er in vielen Begiehungen der Larve von Phoxichilidium, welche den 
Hydroidpolypen verlåsst». In my opinion the peculiarity in Fa//ene emaciata, .the species mentioned 
by Dohrn, is only to be found in the fact that the larva completes its development in the egg, in- 
side the egg shell; and that this fact is not to be understood as something general in the genus, but 
only as a peculiarity in this species among known forms I infer from the fact that in another Pa//ere- 
species, Pa/llene hastata, I have found all larvæ free with only three pairs of developed ambulatory 
legs, pl. I, fig. 18—19. In the nearly related genus Psewdopallene I have even found the larva free im 
its first stage with the two foremost pairs of ambulatory legs not yet quite developed, pl. I, fig.8. In 
the following I shall enter into further details as to this fact. Also in other genera, for inst. in Nym- 
phon, it may be found in the different species that the larvæ leave the egg shell sooner or later, with- 
out any other difference in the course of development. It is quite another thing that a good-bound- 
ary really exists, but it can as usual be placed at the origin of the first larval form, here according- 
ly it is to be applied to the form that has been called «Protonymphon» (Hoek) or «the Pantopod- 
larva» (Dohrn). 
Already in the introduction to this section on the larval development, I spoke of the usual 
misconception with regard to the duration of the embryonal life, and gave a quotation frem the text- 
book by Korschelt and Heider. I have here tried by demonstration on my figures to maintain 
more in detail that all Pycnogonida pass through the same series of larval stages, whether the larva 
«Protonymphon» frees itself at once, or remains in the egg till all the ambulatory legs are developed, 
even if it has not attained its full length, segmentation, or all its appendages. 
When the yolk-division is equal the whole blastoderm, only excepting the 
middle and hinder parts of the dorsal side, participates in the formation of the em- 
bryonal limbs and the proboscis. The embryo is free at once, is considered to be a 
fully developed larva in the first stage, and is called Protonymphon (Hoek) or Pan- 
topod-larva kat exochen (Dohrn, Morgan). 
It is the enormous, overruling development of the embryonal limbs and the proboscis that is 
a characteristic feature of this larval form, and this feature is found spread through the whole system 
of the Pycnogonida, and has been known and described in different genera, as Phoxichilidium, Pycno- 
gonum, Phoxichilus, Ammothea (Acheliay, Ascorhynchus, and Tanystylum. It is also this larval form 
which has originally played the greatest part as to the question of the systematic position of the 
