PYGNOGONIDA. 13 
the belly of the «mother» (the father it ought to be); sometimes the yolk is consumed, and then the 
young one has to find its food. 47 In the third stage the larva gets the fourth and last pair of (ru- 
dimentary) feet. The two preceding pairs (the three preceding must be meant) are very much devel- 
oped. «The maxillæ» (i. e. palps and ovigerous legs) on the contrary, are still, in the species where 
they are found, quite rudimentary. 5” After a new casting of the skin the animal nearly gets its 
permanent shape, although the length of the body and the limbs is altered not a little. 
Dohrun in a couple of works has given important contributions to the history of development, 
first in his: «Untersuchungen uber Bau und Entwickelung der Arthropoden» (1870) in the second sec- 
tion of which, with the sub-title «Ueber Entwickelung der Pycnogoniden», he treats of the develop- 
ment of the larva of Pycrogonum litterale, Achelia lævis and Phoxichilidium sp. Still more important, 
however, is the contribution, he has given in the monograph entitled: «Die Pantopoden des Golfes 
von Neapel» (1881), in which, besides descriptions and figures of many different genera as Barana, 
Ammothea, Clotenia, Phoxichilus, Phoxichilidium and Pallene, he gives an account of the larvæ known 
to him, and their development 1. c. p. 6,6—80. The principal progress in our knowledge of the devel- 
opment given by Dohrn is that he justly shows how Krøyer has been wrong in his interpretation 
of the development of the two foremost pairs of ambulatory legs, as if those pairs had arisen by an 
uninterrupted development of the two hindmost pairs of limbs in the first form of the larva, «the em- 
bryonal legs» as I have called them. Krøyer's error is, I suppose, principally due to the fact that 
in the very young larva of Pa/l/ene (or Pseudopallene) these limbs are almost or entirely wanting, and 
so Krøyer has taken the two foremost pairs of legs (i. e. ambulatory legs) to be corresponding to the 
two foremost pairs of legs (i. e. embryonal legs) in the larva of the other species. In the following I 
shall again recur to this subject. 
The works on the Pycnogonida by Hoek are well known. The two most important are: 
«Report on the Pycnogonida» in the Voyage of H. M. $S. Challenger (1881) in which he on the 
plates XIX and XX represents the larvæ from their earliest development; and next his «Nouvelles 
études sur les Pycnogonides» (1881) where on pl. XXX the different larvæ are represented.  Besides 
figures of well known forms, as Phoxrichilidium, Ammothea and Pycnogonum, he especially draws 
different species of the genus Wymphon. In the lastmentioned treatise, 1. c. p. 481 seq.  Hoek gives 
the results of his examinations in the following way: «Voici en peu de mots le résultat auquel je suis 
arrivé: on trouve toujours, å quelques exceptions prés, comme premiére forme larvaire, un animal avec 
trois paires d'extrémités, dont la premiére se termine en une pince et dont les deux suivantes sont 
formées de deux articles et se terminent par des griffes allongées (larve Protonymphon). Les deux 
derniéres paires d'extrémités sont — comme la premiére paire — des appendices simples, cest-å-dire 
qwelles ne sont pas divisées en deux branches comme celles des larves Nauplius. La bouche est 
placée å la fin d'une excroissance de forme cylindrique ou conique, qui est implantée entre la pre- 
miére et la seconde paire d'appendices: cette excroissance, cest la trompe, qui au moment de Véclosion 
de la larve est toujours træs courte, mais posséde déjå cette forme conique ou cylindrique. 
… La maniére dont VPanimal adulte se développe de cette forme larvaire est des plus simples. 
Tandis que les trois appendices originaux se métamorphosent dans les trois paires d'appendices 
céphaliques ou disparaissent (soit une, soit deux, soit — et ceci »'arrive jamais chez les individus 
