﻿PYGNOGONIDA. 



13 



the bellv of the mother^ (the father it ought to be); soiuetinies the yolk is consumed, and then the 

 young one has to find its food. 4 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. sThe maxillse (i.e. palps and ovigerous legs) on the contrary, are still, in the species where 

 thev 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. 



Dohrn in a couple of works has given important contributions to the history of development, 

 first in his: Untersuchungen iiber Ban 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 Pyciiogoi/iiiit littrrale, ^icliclia hrvis and Phoxichilidiitiii 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^ 

 Amiiiothca, Cloteiiia, PltoxicJiilns , Phoxichilidiiim and Pallc)it\ he gi\es an account of the larvae known 

 to him, and their development I.e. p. 69 — 80. The principal progress in our knowledge of the devel- 

 opment given bv Dohrn is that he justly shows how Kroyer has been wrong in his interpretation 

 of the development of the two foremost pairs of ambulator)- legs, as if those pairs had arisen by an 

 uninterrupted development of the two hindmost pairs of limbs in the first form of the lar\-a, tlie em- 

 brvonal legs as I have called them. Kr oyer's error is, I suppo.se, principally due to the fact that 

 in the very young lar\-a of PgIIdic (or Pscudopallnif) these limbs are almost or entirely wanting, and 

 so Kroyer has taken the two foremost pairs of legs (i.e. ambulator\- legs) to be corresponding to the 

 two foremost pairs of legs (i. e. embr>-onal legs) in the larva of the other species. In the following I 

 shall again recur to this subject. 



The works on the P\cnogonida b\- Hoek are well known. The two most important are: 

 Report on the P>cnogonida in the \'oyage of H. Vl. S. Challenger (1881) in which he on the 

 plates XIX and XX represents the larvae from their earliest development; and next his i.Nouvelles 

 etudes sur les Pycnogonides (1S81) where on pi. XXX the different larvae are represented. Besides 

 figures of well known forms, as P/wxic/iilidiitt/i , Aiiimothca and Pyciiogoii/i/i/ , he especially draws 

 different .species of the genus Xyi/ip/nvi. In the lastmentioned treatise. I.e. p. 4S1 seq. Hoek gives 

 the results of his examinations in the following way : \'oici en pen de mots le resultat auquel je suis 

 arrive: on trouve toujours, a quelques exceptions pres, comme premiere fornie larvaire, un animal avec 

 trois paires d'extremites, dont la premiere se termine en une pince ct dont les deux suivantes sont 

 formees de deux articles et se terminent par des griffes allongees (lar\-e Protonymphon). Les deux 

 dernieres paires d'extremites sont — comme la premiere paire — des appendices simples, c'est-a-dire 

 qu'elles ne sont pas divisees en deux branches comme celles des larves Xauplius. La bouche est 

 placee a la fin d'une excroissance de forme cylindrique on conicjue, qui est implantee entre la pre- 

 miere et la seconde paire d'appendices: cette excroissance, c'esl la trompe, qui an moment de I'eclosion 

 de la larve est toujours tres courte, mais possede deja cette forme conique on cylindrique. 



La maniere dont I'animal adulte se developpe de cette forme larvaire est des plus simples. 

 Tandis que les trois appendices originaux se metamorphosent dans les trois paires d'appendices 

 cephaliques ou dis])arai.ssent (soit une, soit deux, .soit — et ceci n'arrive jamais chez les individus 



